[Merge] Show Incognito tab switcher button on startup

LayoutManagerChrome now observes the TabModelSelector to see
if any Incognito tabs exist during startup.  If so, it signals
to the Layout that the Incognito tab switcher button should be
visible.

BUG=543885
TBR=dtrainor
Review URL: https://codereview.chromium.org/1514503002
Cr-Commit-Position: refs/heads/master@{#364225}

Review URL: https://codereview.chromium.org/1506203009 .

Cr-Commit-Position: refs/branch-heads/2564@{crosswalk-project#311}
Cr-Branched-From: 1283eca-refs/heads/master@{#359700}

chrome/android/java/src/org/chromium/chrome/browser/compositor/layouts/Layout.java

@@ -814,6 +814,15 @@ public void onTabCreated(long time, int tabId, int tabIndex, int sourceTabId,
         }
     }
 
+    /**
+     * Called when the TabModelSelector has been initialized with an accurate tab count.
+     */
+    public void onTabStateInitialized() {
+        for (int i = 0; i < mSceneOverlays.size(); i++) {
+            mSceneOverlays.get(i).tabStateInitialized();
+        }
+    }
+
     /**
      * Called when the current tabModel switched (e.g. standard -> incognito).
      *

chrome/android/java/src/org/chromium/chrome/browser/compositor/layouts/LayoutManager.java

@@ -7,6 +7,7 @@
 import android.graphics.Point;
 import android.graphics.Rect;
 import android.graphics.RectF;
+import android.os.Handler;
 import android.os.SystemClock;
 import android.view.MotionEvent;
 import android.view.View;
@@ -30,6 +31,7 @@
 import org.chromium.chrome.browser.dom_distiller.ReaderModeManagerDelegate;
 import org.chromium.chrome.browser.fullscreen.ChromeFullscreenManager;
 import org.chromium.chrome.browser.fullscreen.FullscreenManager;
+import org.chromium.chrome.browser.tabmodel.EmptyTabModelSelectorObserver;
 import org.chromium.chrome.browser.tabmodel.TabCreatorManager;
 import org.chromium.chrome.browser.tabmodel.TabModelSelector;
 import org.chromium.content.browser.SPenSupport;
@@ -245,6 +247,8 @@ public void init(TabModelSelector selector, TabCreatorManager creator,
         mContentContainer = androidContentContainer;
 
         if (mNextActiveLayout != null) startShowing(mNextActiveLayout, true);
+
+        updateLayoutForTabModelSelector();
     }
 
     /**
@@ -525,4 +529,30 @@ private int getOrientation() {
             return Orientation.PORTRAIT;
         }
     }
+
+    /**
+     * Updates the Layout for the state of the {@link TabModelSelector} after initialization.
+     * If the TabModelSelector is not yet initialized when this function is called, a
+     * {@link TabModelSelectorObserver} is created to listen for when it is ready.
+     */
+    private void updateLayoutForTabModelSelector() {
+        if (mTabModelSelector.isTabStateInitialized() && getActiveLayout() != null) {
+            getActiveLayout().onTabStateInitialized();
+        } else {
+            mTabModelSelector.addObserver(new EmptyTabModelSelectorObserver() {
+                @Override
+                public void onTabStateInitialized() {
+                    if (getActiveLayout() != null) getActiveLayout().onTabStateInitialized();
+
+                    final EmptyTabModelSelectorObserver observer = this;
+                    new Handler().post(new Runnable() {
+                        @Override
+                        public void run() {
+                            mTabModelSelector.removeObserver(observer);
+                        }
+                    });
+                }
+            });
+        }
+    }
 }

chrome/android/java/src/org/chromium/chrome/browser/compositor/overlays/SceneOverlay.java

@@ -64,6 +64,11 @@ SceneOverlayLayer getUpdatedSceneOverlayTree(LayerTitleCache layerTitleCache,
      */
     void tabTitleChanged(int tabId, String title);
 
+    /**
+     * Called when the TabModelSelector has been initialized with an accurate tab count.
+     */
+    void tabStateInitialized();
+
     /**
      * Called when the active {@link TabModel} switched (e.g. standard -> incognito).
      * @param incognito Whether or not the new active model is incognito.

chrome/android/java/src/org/chromium/chrome/browser/compositor/overlays/strip/StripLayoutHelperManager.java

@@ -234,6 +234,11 @@ public boolean updateOverlay(long time, long dt) {
         return getActiveStripLayoutHelper().updateLayout(time, dt);
     }
 
+    @Override
+    public void tabStateInitialized() {
+        updateModelSwitcherButton();
+    }
+
     @Override
     public void tabModelSwitched(boolean incognito) {
         if (incognito == mIsIncognito) return;