[Android] Additional events to observe in TabObserver.

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

Index: chrome/android/java/src/org/chromium/chrome/browser/TabObserver.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/TabObserver.java b/chrome/android/java/src/org/chromium/chrome/browser/TabObserver.java
index f87ca0e189caa63c911aeb319885f17edfed769b..ad96d031ef5bee2f6d9f6047bfbb10938efeecc7 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/TabObserver.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/TabObserver.java
@@ -62,6 +62,18 @@ public interface TabObserver {
     // WebContentsDelegateAndroid methods ---------------------------------------------------------
 
     /**
+     * Called when the contents loading starts.
+     * @param tab The notifying {@link Tab}.
+     */
+    void onLoadStarted(Tab tab);
+
+    /**
+     * Called when the contents loading stops.
+     * @param tab The notifying {@link Tab}.
+     */
+    void onLoadStopped(Tab tab);
+
+    /**
      * Called when the load progress of a {@link Tab} changes.
      * @param tab      The notifying {@link Tab}.
      * @param progress The new progress from [0,100].