[tracing] Add SkResourceCache statistics to chrome://tracing (chrome side)

skia/ext/SkDiscardableMemory_chrome.h

Index: skia/ext/SkDiscardableMemory_chrome.h
diff --git a/skia/ext/SkDiscardableMemory_chrome.h b/skia/ext/SkDiscardableMemory_chrome.h
index 1be4516be168b90648940b5dbb03f13747a29963..93a7807b5f2026e57277eeb5a16d25453486c04b 100644
--- a/skia/ext/SkDiscardableMemory_chrome.h
+++ b/skia/ext/SkDiscardableMemory_chrome.h
@@ -10,8 +10,14 @@
 
 namespace base {
 class DiscardableMemory;
+
+namespace trace_event {
+class MemoryAllocatorDump;
+class ProcessMemoryDump;
 }
 
+}  // namespace base
+
 // This class implements the SkDiscardableMemory interface using
 // base::DiscardableMemory.
 class SK_API SkDiscardableMemoryChrome : public SkDiscardableMemory {
@@ -23,6 +29,10 @@ public:
  void* data() override;
  void unlock() override;
 
+ base::trace_event::MemoryAllocatorDump* CreateMemoryAllocatorDump(
+     const char* name,
+     base::trace_event::ProcessMemoryDump* pmd) const;
+
 private:
   friend class SkDiscardableMemory;