[Android] Fix crashes on Chrome internal pages.

chrome/android/java/src/org/chromium/chrome/browser/compositor/CompositorViewHolder.java

 // Copyright 2015 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.compositor;
 
 import android.content.Context;
 import android.graphics.Canvas;
 import android.graphics.Paint;
 import android.graphics.Rect;
@@ skipping 205 matching lines @@
                 // ContentView's relayout, which causes the ContentView to relayout on top of the
                 // stack view.  The 30ms is arbitrary, hoping to let the view get one repaint
                 // in so the full page is shown.
                 if (mPostHideKeyboardTask != null) {
                     new Handler().postDelayed(mPostHideKeyboardTask, 30);
                     mPostHideKeyboardTask = null;
                 }
             }
         });
 
-        if (!DeviceFormFactor.isTablet(getContext())) mProgressBarDrawingInfo = new DrawingInfo();
         mCompositorView = new CompositorView(getContext(), this);
         addView(mCompositorView,
                 new FrameLayout.LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT));
     }
 
     /**
      * @param layoutManager The {@link LayoutManager} instance that will be driving what
      *                      shows in this {@link CompositorViewHolder}.
      */
     public void setLayoutManager(LayoutManager layoutManager) {
@@ skipping 297 matching lines @@
     }
 
     /**
      * To be called once a frame before commit.
      */
     @Override
     public void onCompositorLayout() {
         TraceEvent.begin("CompositorViewHolder:layout");
         if (mLayoutManager != null) {
             mLayoutManager.onUpdate();
-            if (mProgressBarDrawingInfo != null) {
+
+            if (!DeviceFormFactor.isTablet(getContext()) && mControlContainer != null) {
+                if (mProgressBarDrawingInfo == null) mProgressBarDrawingInfo = new DrawingInfo();
                 mControlContainer.getProgressBarDrawingInfo(mProgressBarDrawingInfo);
+            } else {
+                mProgressBarDrawingInfo = null;

[Ted C, 2015/07/30 15:02:13]

why do you need to set it to null here?

does the drawing code handle it if we go from non-null to null?  Does null clear
out the progress bar or would it leave it drawing the old state?

[Kibeom Kim (inactive), 2015/07/30 17:00:28]

Done.

(Changed to assert since we expect mControlContainer to be initialized only
once, but I can also change to handle clearing)

             }
+
             mCompositorView.finalizeLayers(mLayoutManager, mSkipNextToolbarTextureUpdate,
                     mProgressBarDrawingInfo);
 
             // TODO(changwan): Check if this hack can be removed.
             // This is a hack to draw one more frame if the screen just rotated for Nexus 10 + L.
             // See http://crbug/440469 for more.
             if (mSkipNextToolbarTextureUpdate) {
                 requestRender();
             }
         }
@@ skipping 573 matching lines @@
             if (mPixelRect.width() == 0) {
                 mPixelRect.right = mPixelRect.left + 1;
             }
             if (mPixelRect.height() == 0) {
                 mPixelRect.bottom = mPixelRect.top + 1;
             }
             return mPixelRect;
         }
     }
 }