Adding option for adding new tab in tab manager for chrome shell.

chrome/android/shell/java/src/org/chromium/chrome/shell/ChromeShellTabModelSelector.java

Index: chrome/android/shell/java/src/org/chromium/chrome/shell/ChromeShellTabModelSelector.java
diff --git a/chrome/android/shell/java/src/org/chromium/chrome/shell/ChromeShellTabModelSelector.java b/chrome/android/shell/java/src/org/chromium/chrome/shell/ChromeShellTabModelSelector.java
index 3d54c086b832a7873bd96e2b499eed04e5c18a9f..a6b9e802d5ac501aa710b1ae4c67e1717f4ffdf8 100644
--- a/chrome/android/shell/java/src/org/chromium/chrome/shell/ChromeShellTabModelSelector.java
+++ b/chrome/android/shell/java/src/org/chromium/chrome/shell/ChromeShellTabModelSelector.java
@@ -120,6 +120,7 @@ class ChromeShellTabModelSelector extends TabModelSelectorBase {
      */
     public void hideTabSwitcher() {
         if (mTabModelWrapper == null) return;
+        mTabManager.mToolbar.initializeAddButton(false);

[Bernhard Bauer, 2014/11/05 10:01:53]

Hmm... the encapsulation violation here aside, I'm not very happy for the model
to know about the toolbar and the state of the buttons on it. Really, the
toolbar should observe changes to the model and update itself in reaction.

We could add a method onVisibilityChanged() to the
TabModelSelector.ChangeListener interface and have ChromeShellToolbar implement
that to update its buttons. That would also allow us to move the code that
updates the view here to some place else, like the TabManager. Then the model
would only know about its state and not deal with updating any views.

If we end up doing this, most of my comments below probably don't apply anymore;
I've left them in for completeness.

[divya.bansal, 2014/11/05 12:22:17]

AccessibilityTabModelWrapper implements TabModelSelector.ChangeListener and its
object is initialized in ChromeShellTabModelSelector according to visibility of
tabswitcher mode.
So any method in TabModelSelector.ChangeListener cannot be implemented in
ChromeShellToolbar or ChromeShellToolbarModelSelector. Please suggest that how
to implement it.

[Bernhard Bauer, 2014/11/05 12:36:03]

Why is it a problem that AccessibilityTabModelWrapper implements
TabModelSelector.ChangeListener? Just implement the new method with an empty
body there.

[divya.bansal, 2014/11/07 05:26:26]

@Bernhard I have tried to implement this behaviour in other way using local
objects and methods.
PTAL at new changes.

[divya.bansal, 2014/11/10 13:49:59]

Done. Made changes according to your suggestion. PTAL

         ViewParent parent = mTabModelWrapper.getParent();
         if (parent != null) {
             assert parent == mParent;
@@ -134,10 +135,10 @@ class ChromeShellTabModelSelector extends TabModelSelectorBase {
             mTabModelWrapper.setup(null);
             mTabModelWrapper.setTabModelSelector(this);
         }
-
         if (mTabModelWrapper.getParent() == null) {
             mParent.addView(mTabModelWrapper);
         }
+        mTabManager.mToolbar.initializeAddButton(true);
     }
 
     public boolean isTabSwitcherVisible() {