Bug 1036777 - Remove the useAllocator argument to XPCConvert::JSData2Native; r=bholley

It turns out the useAllocator argument is only used for the dipper types
(nsXPTType::{T_ASTRING, T_DOMSTRING, T_UTF8STRING, T_CSTRING}), while we
only pass true in cases where we don't have a dipper type:

* XPCConvert::JSArray2Native errors on those types;
* GetNamedPropertyAsVariantRaw() passes an interface type;
* nsXPCWrappedJSClass::CallMethod passes !param.IsDipper() for the first
  calls and only reaches the last call for dependent types, which do not
  include any of the dipper types;
* CallMethodHelper::ConvertIndependentParam handles dipper types earlier
* and CallMethodHelper::ConvertDependentParam handles dependent types.

js/xpconnect/src/XPCConvert.cpp

@@ -376,7 +376,7 @@ bool ConvertToPrimitive(JSContext *cx, HandleValue v, T *retval)
 bool
 XPCConvert::JSData2Native(void* d, HandleValue s,
                           const nsXPTType& type,
-                          bool useAllocator, const nsID* iid,
+                          const nsID* iid,
                           nsresult* pErr)
 {
     NS_PRECONDITION(d, "bad param");
@@ -474,10 +474,7 @@ XPCConvert::JSData2Native(void* d, HandleValue s,
     case nsXPTType::T_ASTRING:
     {
         if (s.isUndefined()) {
-            if (useAllocator)
-                *((const nsAString**)d) = &NullString();
-            else
-                (**((nsAString**)d)).SetIsVoid(true);
+            (**((nsAString**)d)).SetIsVoid(true);
             return true;
         }
         // Fall through to T_DOMSTRING case.
@@ -485,10 +482,7 @@ XPCConvert::JSData2Native(void* d, HandleValue s,
     case nsXPTType::T_DOMSTRING:
     {
         if (s.isNull()) {
-            if (useAllocator)
-                *((const nsAString**)d) = &NullString();
-            else
-                (**((nsAString**)d)).SetIsVoid(true);
+            (**((nsAString**)d)).SetIsVoid(true);
             return true;
         }
         size_t length = 0;
@@ -499,27 +493,17 @@ XPCConvert::JSData2Native(void* d, HandleValue s,
             if (!str)
                 return false;
 
-            chars = useAllocator ? JS_GetStringCharsZAndLength(cx, str, &length)
-                                 : JS_GetStringCharsAndLength(cx, str, &length);
+            chars = JS_GetStringCharsAndLength(cx, str, &length);
             if (!chars)
                 return false;
 
             if (!length) {
-                if (useAllocator)
-                    *((const nsAString**)d) = &EmptyString();
-                else
-                    (**((nsAString**)d)).Truncate();
+                (**((nsAString**)d)).Truncate();
                 return true;
             }
         }
 
-        nsString* ws;
-        if (useAllocator) {
-            ws = nsXPConnect::GetRuntimeInstance()->NewShortLivedString();
-            *((const nsString**)d) = ws;
-        } else {
-            ws = *((nsString**)d);
-        }
+        nsString* ws = *((nsString**)d);
 
         if (!str) {
             ws->AssignLiteral(MOZ_UTF16("undefined"));
@@ -531,10 +515,6 @@ XPCConvert::JSData2Native(void* d, HandleValue s,
             // The characters represent a literal char16_t string constant
             // compiled into libxul, such as the string "undefined" above.
             ws->AssignLiteral(chars, length);
-        } else if (useAllocator && STRING_TO_JSVAL(str) == s) {
-            // The JS string will exist over the function call.
-            // We don't need to copy the characters in this case.
-            ws->Rebind(chars, length);
         } else {
             ws->Assign(chars, length);
         }
@@ -615,12 +595,8 @@ XPCConvert::JSData2Native(void* d, HandleValue s,
         JSString* str;
 
         if (s.isNull() || s.isUndefined()) {
-            if (useAllocator) {
-                *((const nsACString**)d) = &NullCString();
-            } else {
-                nsCString* rs = *((nsCString**)d);
-                rs->SetIsVoid(true);
-            }
+            nsCString* rs = *((nsCString**)d);
+            rs->SetIsVoid(true);
             return true;
         }
 
@@ -632,26 +608,12 @@ XPCConvert::JSData2Native(void* d, HandleValue s,
         }
 
         if (!length) {
-            if (useAllocator) {
-                *((const nsACString**)d) = &EmptyCString();
-            } else {
-                nsCString* rs = *((nsCString**)d);
-                rs->Truncate();
-            }
+            nsCString* rs = *((nsCString**)d);
+            rs->Truncate();
             return true;
         }
 
-        nsCString *rs;
-        if (useAllocator) {
-            // Use nsCString to enable sharing
-            rs = new nsCString();
-            if (!rs)
-                return false;
-
-            *((const nsCString**)d) = rs;
-        } else {
-            rs = *((nsCString**)d);
-        }
+        nsCString *rs = *((nsCString**)d);
         CopyUTF16toUTF8(Substring(chars, length), *rs);
         return true;
     }
@@ -659,18 +621,9 @@ XPCConvert::JSData2Native(void* d, HandleValue s,
     case nsXPTType::T_CSTRING:
     {
         if (s.isNull() || s.isUndefined()) {
-            if (useAllocator) {
-                nsACString *rs = new nsCString();
-                if (!rs)
-                    return false;
-
-                rs->SetIsVoid(true);
-                *((nsACString**)d) = rs;
-            } else {
-                nsACString* rs = *((nsACString**)d);
-                rs->Truncate();
-                rs->SetIsVoid(true);
-            }
+            nsACString* rs = *((nsACString**)d);
+            rs->Truncate();
+            rs->SetIsVoid(true);
             return true;
         }
 
@@ -686,25 +639,12 @@ XPCConvert::JSData2Native(void* d, HandleValue s,
         }
 
         if (!length) {
-            if (useAllocator) {
-                *((const nsACString**)d) = &EmptyCString();
-            } else {
-                nsCString* rs = *((nsCString**)d);
-                rs->Truncate();
-            }
+            nsCString* rs = *((nsCString**)d);
+            rs->Truncate();
             return true;
         }
 
-        nsACString *rs;
-        if (useAllocator) {
-            rs = new nsCString();
-            if (!rs)
-                return false;
-            *((const nsACString**)d) = rs;
-        } else {
-            rs = *((nsACString**)d);
-        }
-
+        nsACString *rs = *((nsACString**)d);
         rs->SetLength(uint32_t(length));
         if (rs->Length() != uint32_t(length)) {
             return false;
@@ -1608,7 +1548,7 @@ XPCConvert::JSArray2Native(void** d, HandleValue s,
         for (initedCount = 0; initedCount < count; initedCount++) {            \
             if (!JS_GetElement(cx, jsarray, initedCount, &current) ||          \
                 !JSData2Native(((_t*)array)+initedCount, current, type,        \
-                               true, iid, pErr))                               \
+                               iid, pErr))                                     \
                 goto failure;                                                  \
         }                                                                      \
     PR_END_MACRO

js/xpconnect/src/XPCWrappedJSClass.cpp

@@ -283,10 +283,7 @@ GetNamedPropertyAsVariantRaw(XPCCallContext& ccx,
     RootedValue val(ccx);
 
     return JS_GetPropertyById(ccx, aJSObj, aName, &val) &&
-           // Note that this always takes the T_INTERFACE path through
-           // JSData2Native, so the value passed for useAllocator
-           // doesn't really matter. We pass true for consistency.
-           XPCConvert::JSData2Native(aResult, val, type, true,
+           XPCConvert::JSData2Native(aResult, val, type,
                                      &NS_GET_IID(nsIVariant), pErr);
 }
 
@@ -1350,13 +1347,13 @@ pre_call_clean_up:
     (defined(__powerpc__) && !defined (__powerpc64__)))
         if (type_tag == nsXPTType::T_JSVAL) {
             if (!XPCConvert::JSData2Native(*(void**)(&pv->val), val, type,
-                                           !param.IsDipper(), &param_iid, nullptr))
+                                           &param_iid, nullptr))
                 break;
         } else
 #endif
         {
             if (!XPCConvert::JSData2Native(&pv->val, val, type,
-                                           !param.IsDipper(), &param_iid, nullptr))
+                                           &param_iid, nullptr))
                 break;
         }
     }
@@ -1429,7 +1426,7 @@ pre_call_clean_up:
                     break;
             } else {
                 if (!XPCConvert::JSData2Native(&pv->val, val, type,
-                                               true, &param_iid,
+                                               &param_iid,
                                                nullptr))
                     break;
             }

js/xpconnect/src/XPCWrappedNative.cpp

@@ -2156,7 +2156,7 @@ CallMethodHelper::ConvertIndependentParam(uint8_t i)
     }
 
     nsresult err;
-    if (!XPCConvert::JSData2Native(&dp->val, src, type, true, &param_iid, &err)) {
+    if (!XPCConvert::JSData2Native(&dp->val, src, type, &param_iid, &err)) {
         ThrowBadParam(err, i, mCallContext);
         return false;
     }
@@ -2276,7 +2276,7 @@ CallMethodHelper::ConvertDependentParam(uint8_t i)
             }
         }
     } else {
-        if (!XPCConvert::JSData2Native(&dp->val, src, type, true,
+        if (!XPCConvert::JSData2Native(&dp->val, src, type,
                                        &param_iid, &err)) {
             ThrowBadParam(err, i, mCallContext);
             return false;

js/xpconnect/src/xpcprivate.h

@@ -2501,7 +2501,7 @@ public:
 
     static bool JSData2Native(void* d, JS::HandleValue s,
                               const nsXPTType& type,
-                              bool useAllocator, const nsID* iid,
+                              const nsID* iid,
                               nsresult* pErr);
 
     /**