Use v8::kGCCallbackFlagCollectAllAvailableGarbage in Heap::CollectAllAvailableGarbage

Now that the embedder side supports v8::kGCCallbackFlagCollectAllAvailableGarbage,
this CL removes the old v8::kGCCallbackFlagForced from Heap::CollectAllAvailableGarbage.

BUG=591463
LOG=Y

Review URL: https://codereview.chromium.org/1762313002

Cr-Commit-Position: refs/heads/master@{#34517}

src/heap/heap.cc

@@ -895,7 +895,7 @@ void Heap::CollectAllAvailableGarbage(const char* gc_reason) {
   const int kMinNumberOfAttempts = 2;
   for (int attempt = 0; attempt < kMaxNumberOfAttempts; attempt++) {
     if (!CollectGarbage(MARK_COMPACTOR, gc_reason, NULL,
-                        v8::kGCCallbackFlagForced) &&
+                        v8::kGCCallbackFlagCollectAllAvailableGarbage) &&
         attempt + 1 >= kMinNumberOfAttempts) {
       break;
     }