[tracing] Expose memory-infra tracing infrastructure to Blink.

public/platform/Platform.h

Index: public/platform/Platform.h
diff --git a/public/platform/Platform.h b/public/platform/Platform.h
index b8598e36665f9128c1a0cc67a3f998547a213b9f..55ce2fca75f81c13ccc93a5481afb3382780dee8 100644
--- a/public/platform/Platform.h
+++ b/public/platform/Platform.h
@@ -83,6 +83,7 @@ class WebMIDIAccessor;
 class WebMIDIAccessorClient;
 class WebMediaStreamCenter;
 class WebMediaStreamCenterClient;
+class WebMemoryDumpProvider;
 class WebMessagePortChannel;
 class WebMimeRegistry;
 class WebNavigatorConnectProvider;
@@ -556,6 +557,15 @@ public:
     virtual void recordRappor(const char* metric, const WebString& sample) { }
     virtual void recordRapporURL(const char* metric, const blink::WebURL& url) { }
 
+    // Registers a memory dump provider. The WebMemoryDumpProvider::onMemoryDump
+    // method will be called on the same thread that called the
+    // registerMemoryDumpProvider() method.
+    // See crbug.com/458295 for design docs.
+    virtual void registerMemoryDumpProvider(blink::WebMemoryDumpProvider*) { }
+
+    // Must be called on the thread that called registerMemoryDumpProvider().
+    virtual void unregisterMemoryDumpProvider(blink::WebMemoryDumpProvider*) { }
+
     // GPU ----------------------------------------------------------------
     //
     // May return null if GPU is not supported.