Remove custom counts histogram from the blink API.

content/child/blink_platform_impl.h

Index: content/child/blink_platform_impl.h
diff --git a/content/child/blink_platform_impl.h b/content/child/blink_platform_impl.h
index 141868981b8d46995fa2ff22574d9fe0c05da060..52b8e3e213727713e3b8f73bd1de4769288a00de 100644
--- a/content/child/blink_platform_impl.h
+++ b/content/child/blink_platform_impl.h
@@ -109,11 +109,6 @@ class CONTENT_EXPORT BlinkPlatformImpl
       blink::WebWaitableEvent::InitialState state) override;
   blink::WebWaitableEvent* waitMultipleEvents(
       const blink::WebVector<blink::WebWaitableEvent*>& events) override;
-  void histogramCustomCounts(const char* name,
-                             int sample,
-                             int min,
-                             int max,
-                             int bucket_count) override;
   void histogramEnumeration(const char* name,
                             int sample,
                             int boundary_value) override;