Add onBackgroundColorChanged to Tab and TabObserver

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

Index: chrome/android/java/src/org/chromium/chrome/browser/Tab.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/Tab.java b/chrome/android/java/src/org/chromium/chrome/browser/Tab.java
index 105ec3be65f85779b39df55f10db56604e05c873..3539fe20a995acf41d4eba33533ff6e798ab7b29 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/Tab.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/Tab.java
@@ -1034,6 +1034,14 @@ public class Tab {
     }
 
     /**
+     * Called when the background color for the content changes.
+     * @param color The current for the background.
+     */
+    protected void onBackgroundColorChanged(int color) {
+        for (TabObserver observer : mObservers) observer.onBackgroundColorChanged(this, color);
+    }
+
+    /**
      * Destroys the current {@link ContentViewCore}.
      * @param deleteNativeWebContents Whether or not to delete the native WebContents pointer.
      */