Added UMA stat for tracking accidental navigations on double tap.

chrome/android/java/src/org/chromium/chrome/browser/TabBase.java

Index: chrome/android/java/src/org/chromium/chrome/browser/TabBase.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/TabBase.java b/chrome/android/java/src/org/chromium/chrome/browser/TabBase.java
index ea58f094cbbd653757d641b14ee0410aedb7d321..c326d1c1b5e6fc30a94926f9d48d5c1cffd2d543 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/TabBase.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/TabBase.java
@@ -224,7 +224,11 @@ public abstract class TabBase implements NavigationClient {
      * Goes to the navigation entry before the current one.
      */
     public void goBack() {
-        if (mContentViewCore != null) mContentViewCore.goBack();
+        if (mContentViewCore != null) {
+            mContentViewCore.reportActionAfterDoubleTapUMA(
+                ContentViewCore.UMAActionAfterDoubleTap.NAVIGATE_BACK);
+            mContentViewCore.goBack();
+        }
     }
 
     /**
@@ -335,7 +339,11 @@ public abstract class TabBase implements NavigationClient {
 
     /** Stop the current navigation. */
     public void stopLoading() {
-        if (mContentViewCore != null) mContentViewCore.stopLoading();
+        if (mContentViewCore != null) {
+            mContentViewCore.reportActionAfterDoubleTapUMA(
+                ContentViewCore.UMAActionAfterDoubleTap.NAVIGATE_STOP);
+            mContentViewCore.stopLoading();
+        }
     }
 
     /**