Add onBackgroundColorChanged to Tab and 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 224b94ab60f2b0c302e057cbfa138620746e6dad..226a7e5e76d3a9f7072e4dd511e47139049bb6f0 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/TabObserver.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/TabObserver.java
@@ -195,6 +195,13 @@ public interface TabObserver {
      */
     public void onDidDetachInterstitialPage(Tab tab);
 
+    /**
+     * Called when the background color for the tab has changed.
+     * @param tab The notifying {@link Tab}.
+     * @param color The current background color.
+     */
+    public void onBackgroundColorChanged(Tab tab, int color);
+
     public void webContentsCreated(Tab tab, long sourceWebContents, long openerRenderFrameId,
             String frameName, String targetUrl, long newWebContents);
 }