Remove Sparse Histograms from Blink Platform API.

third_party/WebKit/public/platform/Platform.h

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 435 matching lines @@
     // Testing -------------------------------------------------------------
 
     // Get a pointer to testing support interfaces. Will not be available in production builds.
     virtual WebUnitTestSupport* unitTestSupport() { return nullptr; }
 
     // Callbacks for reporting histogram data.
     // CustomCounts histogram has exponential bucket sizes, so that min=1, max=1000000, bucketCount=50 would do.
     virtual void histogramCustomCounts(const char* name, int sample, int min, int max, int bucketCount) { }
     // Enumeration histogram buckets are linear, boundaryValue should be larger than any possible sample value.
     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 a RAPPOR privacy-preserving metric, see: https://www.chromium.org/developers/design-documents/rappor.
     // recordRappor records a sample string, while recordRapporURL records the domain and registry of a url.
     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. |name| is used for debugging
     // (duplicates are allowed) and must be a long-lived C string.
@@ skipping 180 matching lines @@
 protected:
     BLINK_PLATFORM_EXPORT Platform();
     virtual ~Platform() { }
 
     WebThread* m_mainThread;
 };
 
 } // namespace blink
 
 #endif