Simple BlinkGC heap compaction.

third_party/WebKit/Source/platform/heap/ThreadState.h

Index: third_party/WebKit/Source/platform/heap/ThreadState.h
diff --git a/third_party/WebKit/Source/platform/heap/ThreadState.h b/third_party/WebKit/Source/platform/heap/ThreadState.h
index 4f04eb71dabdfa9b7ba3fd19a7f162bb88e87fbb..8487fa50e8d16328d44b12ec9e15cc1943dcb6b1 100644
--- a/third_party/WebKit/Source/platform/heap/ThreadState.h
+++ b/third_party/WebKit/Source/platform/heap/ThreadState.h
@@ -285,6 +285,8 @@ class PLATFORM_EXPORT ThreadState {
   // the executions of mutators.
   void makeConsistentForMutator();
 
+  void compact();
+
   // Support for disallowing allocation. Mainly used for sanity
   // checks asserts.
   bool isAllocationAllowed() const {
@@ -322,6 +324,19 @@ class PLATFORM_EXPORT ThreadState {
     ThreadState* const m_threadState;
   };
 
+  class GCForbiddenScope final {
+    STACK_ALLOCATED();
+
+   public:
+    GCForbiddenScope(ThreadState* threadState) : m_threadState(threadState) {
+      m_threadState->enterGCForbiddenScope();
+    }
+    ~GCForbiddenScope() { m_threadState->leaveGCForbiddenScope(); }
+
+   private:
+    ThreadState* const m_threadState;
+  };
+
   void flushHeapDoesNotContainCacheIfNeeded();
 
   // Safepoint related functionality.
@@ -561,6 +576,8 @@ class PLATFORM_EXPORT ThreadState {
 
   v8::Isolate* isolate() const { return m_isolate; }
 
+  BlinkGC::StackState stackState() const { return m_stackState; }
+
   void collectGarbage(BlinkGC::StackState, BlinkGC::GCType, BlinkGC::GCReason);
   void collectGarbageForTerminatingThread();
   void collectAllGarbage();