Collect host of Web Component usage to send to RAPPOR

public/platform/Platform.h

Index: public/platform/Platform.h
diff --git a/public/platform/Platform.h b/public/platform/Platform.h
index 13e2cf3d3e30a9711b5a9c4178431178543f7204..c30e8d260c924fd0f1bf3ef4b6b7e84bfa786c7f 100644
--- a/public/platform/Platform.h
+++ b/public/platform/Platform.h
@@ -542,7 +542,8 @@ public:
     virtual void histogramEnumeration(const char* name, int sample, int boundaryValue) { }
     // Unlike enumeration histograms, sparse histograms only allocate memory for non-empty buckets.
     virtual void histogramSparse(const char* name, int sample) { }
-
+    // Record to RAPPOR.
+    virtual void recordRappor(const char* metric, const WebString& sample) { }
 
     // GPU ----------------------------------------------------------------
     //