Add a setter/getter for Launcher.mAllAppsButton.

Also, handle clicks on the all apps button by using onClick() method in
Launcher instead of directly calling onClickAllAppsButton in Hotseat.java

Bug 12553852
Change-Id: I261c27d3e964bbb1f52c2ab610997defd99a59bd

src/com/android/launcher3/Hotseat.java

@@ -156,15 +156,9 @@ public class Hotseat extends FrameLayout {
             allAppsButton.setContentDescription(context.getString(R.string.all_apps_button_label));
             if (mLauncher != null) {
                 allAppsButton.setOnTouchListener(mLauncher.getHapticFeedbackTouchListener());
+                mLauncher.setAllAppsButton(allAppsButton);
+                allAppsButton.setOnClickListener(mLauncher);
             }
-            allAppsButton.setOnClickListener(new View.OnClickListener() {
-                @Override
-                public void onClick(android.view.View v) {
-                    if (mLauncher != null) {
-                        mLauncher.onClickAllAppsButton(v);
-                    }
-                }
-            });
 
             // Note: We do this to ensure that the hotseat is always laid out in the orientation of
             // the hotseat in order regardless of which orientation they were added

src/com/android/launcher3/Launcher.java

@@ -1333,6 +1333,17 @@ public class Launcher extends Activity
         }
     }
 
+    /**
+     * Sets the all apps button. This method is called from {@link Hotseat}.
+     */
+    public void setAllAppsButton(View allAppsButton) {
+        mAllAppsButton = allAppsButton;
+    }
+
+    public View getAllAppsButton() {
+        return mAllAppsButton;
+    }
+
     /**
      * Creates a view representing a shortcut.
      *