Oilpan: introduce sticky forcedForTesting flag to ensure that a precise

Source/heap/ThreadState.h

Index: Source/heap/ThreadState.h
diff --git a/Source/heap/ThreadState.h b/Source/heap/ThreadState.h
index 3e799158c144d011152f6ef167165fbfacc7b935..9671e111f78b11a192d731838da9a0fe1e0920f6 100644
--- a/Source/heap/ThreadState.h
+++ b/Source/heap/ThreadState.h
@@ -278,6 +278,17 @@ public:
     void setGCRequested();
     void clearGCRequested();
 
+    void performPendingGC(StackState);

[wibling-chromium, 2014/04/01 13:26:09]

NIT: Could be made private.

[Mads Ager (chromium), 2014/04/01 13:45:38]

Done.

+
+    // Was the last GC forced for testing? This is set when garbage collection
+    // is forced for testing and there are pointers on the stack. It remains
+    // set until a garbage collection is triggered with no pointers on the stack.
+    // This is used for layout tests that trigger GCs and check if objects are
+    // dead at a given point in time. That only reliably works when we get
+    // precise GCs with no conservative stack scanning.
+    void setForcedForTesting(bool);
+    bool forcedForTesting();

[wibling-chromium, 2014/04/01 13:26:09]

NIT: Could be made private.

[Mads Ager (chromium), 2014/04/01 13:45:38]

This one is called from Heap. We could make heap a friend to hide some of these.
However, that goes for a lot of stuff here, so let's do that as a separate
change?

+
     bool sweepRequested();
     void setSweepRequested();
     void clearSweepRequested();
@@ -540,6 +551,7 @@ private:
     bool m_atSafePoint;
     Vector<Interruptor*> m_interruptors;
     bool m_gcRequested;
+    bool m_forcedForTesting;
     volatile int m_sweepRequested;
     bool m_sweepInProgress;
     size_t m_noAllocationCount;