Implementation of GetFavicon for current tab.

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

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package org.chromium.chrome.browser;
 
 import android.app.Activity;
 import android.content.Context;
 import android.graphics.Bitmap;
 import android.graphics.Color;
@@ skipping 862 matching lines @@
     @CalledByNative
     public String getTitle() {
         if (mNativePage != null) return mNativePage.getTitle();
         if (mContentViewCore != null) return mContentViewCore.getTitle();
         return "";
     }
 
     /**
      * @return The bitmap of the favicon scaled to 16x16dp. null if no favicon
      *         is specified or it requires the default favicon.
-     *         TODO(bauerb): Upstream implementation.
      */
     public Bitmap getFavicon() {

[David Trainor- moved to gerrit, 2014/07/07 17:59:04]

We need to make sure this bitmap is scaled to 16x16dp here (given the javadoc). 
Can we Check the width and height of the returned bitmap and if they aren't
16x16 dp we scale them to that size?  We could also do this in native with the
other scaling.

Also, it might be nice to cache the favicon in this class (as well as the URL we
were on when we last grabbed the favicon).  If the cached URL doesn't match the
current URL here we could invalidate the cached value.  We could also invalidate
it in onFaviconUpdated as well.

[Jitu( very slow this week), 2014/07/09 11:07:11]

I have changed the bitmap to 16x16 in native side.

As per the current implementation once we get the callback onFaviconUpdated()
application can call GetFavicon() to get the icon for current tab.

Regarding your 2nd comment for caching the favicon and the URL,
I have one queries

What if the favicon image changed in for the website, still we holds the old
favicon icon as current Tab cached URL matches the current URL.

Plz correct me if i am wrong.
 

-        return null;
+        if (mNativeTabAndroid == 0)
+            return null;
+        return nativeGetFavicon(mNativeTabAndroid);
     }
 
     /**
      * Loads the tab if it's not loaded (e.g. because it was killed in background).
      * @return true iff tab load was triggered
      */
     @CalledByNative
     public boolean loadIfNeeded() {
         return false;
     }
@@ skipping 247 matching lines @@
     private native void nativeDestroyWebContents(long nativeTabAndroid, boolean deleteNative);
     private native WebContents nativeGetWebContents(long nativeTabAndroid);
     private native Profile nativeGetProfileAndroid(long nativeTabAndroid);
     private native int nativeLoadUrl(long nativeTabAndroid, String url, String extraHeaders,
             byte[] postData, int transition, String referrerUrl, int referrerPolicy,
             boolean isRendererInitiated);
     private native int nativeGetSecurityLevel(long nativeTabAndroid);
     private native void nativeSetActiveNavigationEntryTitleForUrl(long nativeTabAndroid, String url,
             String title);
     private native boolean nativePrint(long nativeTabAndroid);
+    private native Bitmap nativeGetFavicon(long nativeTabAndroid);
 }