Bug 1194426 - Add sourceLength and functionDisplayNameLength to JS::ubi::StackFrame. r=sfink

js/public/UbiNode.h

@@ -363,6 +363,10 @@ class StackFrame : public JS::Traceable {
     // terminated. Returns how many characters were written into the buffer.
     size_t functionDisplayName(RangedPtr<char16_t> destination, size_t length) const;
 
+    // Get the size of the respective strings. 0 is returned for null strings.
+    size_t sourceLength();
+    size_t functionDisplayNameLength();
+
     // JS::Traceable implementation just forwards to our virtual trace method.
     static void trace(StackFrame* frame, JSTracer* trc) {
         if (frame)

js/src/vm/UbiNode.cpp

@@ -112,6 +112,37 @@ StackFrame::functionDisplayName(RangedPtr<char16_t> destination, size_t length)
     return functionDisplayName().match(m);
 }
 
+struct LengthMatcher
+{
+    using ReturnType = size_t;
+
+    size_t
+    match(JSAtom* atom)
+    {
+        return atom ? atom->length() : 0;
+    }
+
+    size_t
+    match(const char16_t* chars)
+    {
+        return chars ? js_strlen(chars) : 0;
+    }
+};
+
+size_t
+StackFrame::sourceLength()
+{
+    LengthMatcher m;
+    return source().match(m);
+}
+
+size_t
+StackFrame::functionDisplayNameLength()
+{
+    LengthMatcher m;
+    return functionDisplayName().match(m);
+}
+
 // All operations on null ubi::Nodes crash.
 const char16_t* Concrete<void>::typeName() const   { MOZ_CRASH("null ubi::Node"); }
 JS::Zone* Concrete<void>::zone() const             { MOZ_CRASH("null ubi::Node"); }