[oilpan] Fix logging in ThreadState

Move away from WTF DataLogF to VLOG

Usage:
  chrome --enable-logging=stderr --vmodule=*/heap/*=1

Change-Id: I379bb4fffa42986ce3efe593bd63547d12afef6e
Reviewed-on: https://chromium-review.googlesource.com/834509Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#525289}

third_party/WebKit/Source/platform/heap/Heap.cpp

@@ -146,6 +146,12 @@ void ThreadHeapStats::DecreaseAllocatedSpace(size_t delta) {
   ProcessHeap::DecreaseTotalAllocatedSpace(delta);
 }
 
+double ThreadHeapStats::LiveObjectRateSinceLastGC() const {
+  if (ObjectSizeAtLastGC() > 0)
+    return static_cast<double>(MarkedObjectSize()) / ObjectSizeAtLastGC();
+  return 0.0;
+}
+
 ThreadHeap::ThreadHeap(ThreadState* thread_state)
     : thread_state_(thread_state),
       region_tree_(std::make_unique<RegionTree>()),

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

@@ -179,11 +179,12 @@ class ThreadHeapStats {
   void DecreaseAllocatedObjectSize(size_t delta);
   size_t AllocatedObjectSize() { return allocated_object_size_; }
   void IncreaseMarkedObjectSize(size_t delta);
-  size_t MarkedObjectSize() { return marked_object_size_; }
+  size_t MarkedObjectSize() const { return marked_object_size_; }
   void IncreaseAllocatedSpace(size_t delta);
   void DecreaseAllocatedSpace(size_t delta);
   size_t AllocatedSpace() { return allocated_space_; }
-  size_t ObjectSizeAtLastGC() { return object_size_at_last_gc_; }
+  size_t ObjectSizeAtLastGC() const { return object_size_at_last_gc_; }
+  double LiveObjectRateSinceLastGC() const;
   void IncreaseWrapperCount(size_t delta) { wrapper_count_ += delta; }
   void DecreaseWrapperCount(size_t delta) { wrapper_count_ -= delta; }
   size_t WrapperCount() { return AcquireLoad(&wrapper_count_); }

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

@@ -508,8 +508,6 @@ class PLATFORM_EXPORT ThreadState {
     }
   };
 
-  static const char* GcReasonString(BlinkGC::GCReason);
-
   // Returns |true| if |object| resides on this thread's heap.
   // It is well-defined to call this method on any heap allocated
   // reference, provided its associated heap hasn't been detached