Bug 911889. Part 5. Add API to detect whether an nsRefreshDriver is in the middle of a refresh. r=dbaron

--HG--
extra : rebase_source : 3cb0dccfe176b5f6d79fd0898ddf6e5a8bed2e39

layout/base/nsRefreshDriver.cpp

@@ -26,7 +26,7 @@
 #endif
 
 #include "mozilla/Util.h"
-
+#include "mozilla/AutoRestore.h"
 #include "nsRefreshDriver.h"
 #include "nsITimer.h"
 #include "nsLayoutUtils.h"
@@ -685,7 +685,8 @@ nsRefreshDriver::nsRefreshDriver(nsPresContext* aPresContext)
     mThrottled(false),
     mTestControllingRefreshes(false),
     mViewManagerFlushIsPending(false),
-    mRequestedHighPrecision(false)
+    mRequestedHighPrecision(false),
+    mInRefresh(false)
 {
   mMostRecentRefreshEpochTime = JS_Now();
   mMostRecentRefresh = TimeStamp::Now();
@@ -1061,6 +1062,9 @@ nsRefreshDriver::Tick(int64_t aNowEpoch, TimeStamp aNowTime)
 
   profiler_tracing("Paint", "RD", TRACING_INTERVAL_START);
 
+  AutoRestore<bool> restoreInRefresh(mInRefresh);
+  mInRefresh = true;
+
   /*
    * The timer holds a reference to |this| while calling |Notify|.
    * However, implementations of |WillRefresh| are permitted to destroy
@@ -1220,6 +1224,8 @@ nsRefreshDriver::Tick(int64_t aNowEpoch, TimeStamp aNowTime)
     mPostRefreshObservers[i]->DidRefresh();
   }
   profiler_tracing("Paint", "RD", TRACING_INTERVAL_END);
+
+  NS_ASSERTION(mInRefresh, "Still in refresh");
 }
 
 /* static */ PLDHashOperator

layout/base/nsRefreshDriver.h

@@ -249,6 +249,8 @@ public:
    */
   static int32_t DefaultInterval();
 
+  bool IsInRefresh() { return mInRefresh; }
+
 private:
   typedef nsTObserverArray<nsARefreshObserver*> ObserverArray;
   typedef nsTHashtable<nsISupportsHashKey> RequestTable;
@@ -302,6 +304,7 @@ private:
   bool mTestControllingRefreshes;
   bool mViewManagerFlushIsPending;
   bool mRequestedHighPrecision;
+  bool mInRefresh;
 
   int64_t mMostRecentRefreshEpochTime;
   mozilla::TimeStamp mMostRecentRefresh;