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

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

Index: chrome/android/shell/java/src/org/chromium/chrome/shell/ChromeShellToolbar.java
diff --git a/chrome/android/shell/java/src/org/chromium/chrome/shell/ChromeShellToolbar.java b/chrome/android/shell/java/src/org/chromium/chrome/shell/ChromeShellToolbar.java
index 4e0eefd4949e0a2160783c0a733b1296f320e75a..74619f9173f90f557b52a85ea0beedfb59d5e64c 100644
--- a/chrome/android/shell/java/src/org/chromium/chrome/shell/ChromeShellToolbar.java
+++ b/chrome/android/shell/java/src/org/chromium/chrome/shell/ChromeShellToolbar.java
@@ -73,6 +73,7 @@ public class ChromeShellToolbar extends LinearLayout {
     private SuggestionPopup mSuggestionPopup;
 
     private ImageButton mStopReloadButton;
+    private ImageButton mAddButton;
     private int mProgress = 0;
     private boolean mLoading = true;
 
@@ -144,6 +145,7 @@ public class ChromeShellToolbar extends LinearLayout {
         initializeTabSwitcherButton();
         initializeMenuButton();
         initializeStopReloadButton();
+        initializeAddButton();
     }
 
     void setMenuHandler(AppMenuHandler menuHandler) {
@@ -247,6 +249,25 @@ public class ChromeShellToolbar extends LinearLayout {
         });
     }
 
+    private void initializeAddButton() {
+        mAddButton = (ImageButton) findViewById(R.id.add_button);
+        mAddButton.setOnClickListener(new OnClickListener() {
+            @Override
+            public void onClick(View v) {
+                mTabManager.createNewTab();
+            }
+        });
+    }
+
+    /**
+     * Shows or hides the add and the stop/reload button .
+     * @param visibility The visibility status of the add button.
+     */
+    public void showAddButton(boolean visibility) {
+        mAddButton.setVisibility(visibility ? VISIBLE : GONE);
+        mStopReloadButton.setVisibility(visibility ? GONE : VISIBLE);
+    }
+
     /**
      * @return Current tab that is shown by ChromeShell.
      */