Added UMA stat for tracking accidental navigations on double tap.

content/browser/android/content_view_core_impl.cc

Index: content/browser/android/content_view_core_impl.cc
diff --git a/content/browser/android/content_view_core_impl.cc b/content/browser/android/content_view_core_impl.cc
index 39fd2f5bbb36e7570aae6c6b29b3d2f5da5a1797..081784d6c98a41eb75420cd1e06232674f014d0f 100644
--- a/content/browser/android/content_view_core_impl.cc
+++ b/content/browser/android/content_view_core_impl.cc
@@ -11,6 +11,7 @@
 #include "base/command_line.h"
 #include "base/json/json_writer.h"
 #include "base/logging.h"
+#include "base/metrics/histogram.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/values.h"
 #include "cc/layers/layer.h"
@@ -1612,6 +1613,25 @@ void ContentViewCoreImpl::SetAccessibilityEnabled(JNIEnv* env, jobject obj,
   }
 }
 
+void ContentViewCoreImpl::SendActionAfterDoubleTapUma(
+    JNIEnv* env,
+    jobject obj,
+    int type,
+    bool hasDelay) {
+  // This UMA stat tracks a user's action after a double tap within
+  // k seconds (where k == 5 currently). This UMA will tell us if
+  // removing the tap gesture delay will lead to significantly more
+  // accidental navigations after a double tap

[Rick Byers, 2013/10/31 17:53:10]

nit - missing .

[bokan, 2013/10/31 22:31:58]

Done.

+  if(hasDelay) {
+      UMA_HISTOGRAM_ENUMERATION("UserInput.ActionAfterDoubleTapWithDelay",
+        type, 3);

[Rick Byers, 2013/10/31 17:53:10]

ugh - hard-coding this 3 is a little unfortunate, but I see the java/native
boundary makes it awkward to do the normal 'MAX' enum thing.  How about just
adding a comment to the enum definition saying to change this line if more
elements are added.

[bokan, 2013/10/31 22:31:58]

It's already there :). But I've gone further and just made the count a param
into this function so updating the enum will be enough.

+  } else {
+      UMA_HISTOGRAM_ENUMERATION("UserInput.ActionAfterDoubleTapNoDelay",
+        type, 3);
+  }
+
+}
+
 void ContentViewCoreImpl::SendOrientationChangeEventInternal() {
   RenderWidgetHostViewAndroid* rwhv = GetRenderWidgetHostViewAndroid();
   if (rwhv)