NTP: fix bad layout when navigating back from a page with a theme-color.

chrome/android/java/src/org/chromium/chrome/browser/ntp/NewTabPageLayout.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.ntp;
 
 import android.content.Context;
 import android.content.res.Resources;
 import android.util.AttributeSet;
 import android.view.View;
@@ skipping 43 matching lines @@
      */
     public NewTabPageLayout(Context context, AttributeSet attrs) {
         super(context, attrs);
         Resources res = getResources();
         float density = res.getDisplayMetrics().density;
         mTopSpacerIdealHeight = Math.round(density * TOP_SPACER_HEIGHT_DP);
         mMiddleSpacerIdealHeight = Math.round(density * MIDDLE_SPACER_HEIGHT_DP);
         mBottomSpacerIdealHeight = Math.round(density * BOTTOM_SPACER_HEIGHT_DP);
         mTotalSpacerIdealHeight = Math.round(density * TOTAL_SPACER_HEIGHT_DP);
         mMostVisitedLayoutBleed = res.getDimensionPixelSize(R.dimen.most_visited_layout_bleed);
-
-        mPeekingCardHeight = getResources()
-                .getDimensionPixelSize(R.dimen.snippets_padding_and_peeking_card_height);
-        mTabStripHeight = getResources().getDimensionPixelSize(R.dimen.tab_strip_height);
+        mPeekingCardHeight =
+                res.getDimensionPixelSize(R.dimen.snippets_padding_and_peeking_card_height);
+        mTabStripHeight = res.getDimensionPixelSize(R.dimen.tab_strip_height);
     }
 
     @Override
     protected void onFinishInflate() {
         super.onFinishInflate();
         mTopSpacer = findViewById(R.id.ntp_top_spacer);
         mMiddleSpacer = findViewById(R.id.ntp_middle_spacer);
         mBottomSpacer = findViewById(R.id.ntp_bottom_spacer);
         mScrollCompensationSpacer = findViewById(R.id.ntp_scroll_spacer);
         mSearchProviderLogoView = (LogoView) findViewById(R.id.search_provider_logo);
@@ skipping 17 matching lines @@
     /**
      * Sets whether the cards UI is enabled.
      * This view assumes that a peeking card will always be present when the cards UI is used.
      */
     public void setUseCardsUiEnabled(boolean useCardsUi) {
         mCardsUiEnabled = useCardsUi;
     }
 
     @Override
     protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
+        // Remove the scroll spacer from the layout so the weighted children can be measured
+        // correctly.
         mScrollCompensationSpacer.setVisibility(View.GONE);
         super.onMeasure(widthMeasureSpec, heightMeasureSpec);
 
         if (getMeasuredHeight() > mParentViewportHeight) {
             // This layout is bigger than its parent's viewport, so the user will need to scroll
             // to see all of it. Extra spacing should be added at the bottom so the user can scroll
             // until Most Visited is at the top.
 
-            // All the spacers have height 0 since they use weights to set height.
+            // The top, middle, and bottom spacers should have a measured height of 0 at this point
+            // since they use weights to set height, and there was no extra space.
             assert mTopSpacer.getMeasuredHeight() == 0;
+            assert mMiddleSpacer.getMeasuredHeight() == 0;
+            assert mBottomSpacer.getMeasuredHeight() == 0;
 
             final int topOfMostVisited = calculateTopOfMostVisited();
             final int belowTheFoldHeight = getMeasuredHeight() - mParentViewportHeight;
             if (belowTheFoldHeight < topOfMostVisited) {
                 mScrollCompensationSpacer.getLayoutParams().height =
                         topOfMostVisited - belowTheFoldHeight;
 
                 if (mCardsUiEnabled) {
                     // If we have a peeking card, allow that to show at the bottom of the screen.
                     mScrollCompensationSpacer.getLayoutParams().height -= mPeekingCardHeight;
                 }
 
+                // Include the scroll spacer in the layout and call super.onMeasure again so it is
+                // measured.
                 mScrollCompensationSpacer.setVisibility(View.INVISIBLE);
                 super.onMeasure(widthMeasureSpec, heightMeasureSpec);
             }
         } else {
-            // This layout is smaller than it's parent viewport, redistribute the extra space.
+            // This layout is smaller than or equal to its parent viewport. Redistribute any
+            // weighted space.
             if (mCardsUiEnabled) {
-                getLayoutParams().height = Math.max(getMeasuredHeight(),
+                // Call super.onMeasure with mode EXACTLY and the target height to allow the top
+                // spacer (which has a weight of 1) to grow and take up the remaining space.
+                int targetHeight = Math.max(getMeasuredHeight(),
                         mParentViewportHeight - mPeekingCardHeight - mTabStripHeight);
-                // Call onMeasure to update mTopScaper's height.
+                heightMeasureSpec = MeasureSpec.makeMeasureSpec(targetHeight, MeasureSpec.EXACTLY);
                 super.onMeasure(widthMeasureSpec, heightMeasureSpec);
             }
             distributeExtraSpace(mTopSpacer.getMeasuredHeight());
         }
 
         // Make the search box and logo as wide as the most visited items.
         if (mMostVisitedLayout.getVisibility() != GONE) {
             final int width = mMostVisitedLayout.getMeasuredWidth() - mMostVisitedLayoutBleed;
-            setMeasure(mSearchBoxView, width + mSearchboxViewShadowWidth,
+            measureExactly(mSearchBoxView, width + mSearchboxViewShadowWidth,
                     mSearchBoxView.getMeasuredHeight());
-            setMeasure(mSearchProviderLogoView, width, mSearchProviderLogoView.getMeasuredHeight());
+            measureExactly(
+                    mSearchProviderLogoView, width, mSearchProviderLogoView.getMeasuredHeight());
         }
     }
 
     /**
      * Calculate the vertical position of Most Visited.
      * This method does not use mMostVisitedLayout.getTop(), so can be called in onMeasure.
      */
     private int calculateTopOfMostVisited() {
         // Manually add the heights (and margins) of all children above Most Visited.
         int top = 0;
@@ skipping 33 matching lines @@
 
         mSearchBoxView.setBackgroundResource(R.drawable.textbox);
         mSearchBoxView.setPadding(
                 resources.getDimensionPixelSize(R.dimen.ntp_search_box_material_padding_left),
                 resources.getDimensionPixelSize(R.dimen.ntp_search_box_material_padding_top),
                 resources.getDimensionPixelSize(R.dimen.ntp_search_box_material_padding_right),
                 resources.getDimensionPixelSize(R.dimen.ntp_search_box_material_padding_bottom));
     }
 
     /**
-     * Distribute extra vertical space between the three spacer views.
+     * Distribute extra vertical space between the three spacer views. Doing this here allows for
+     * more sophisticated constraints than in xml.
      * @param extraHeight The amount of extra space, in pixels.
      */
     private void distributeExtraSpace(int extraHeight) {
         int topSpacerHeight;
         int middleSpacerHeight;
         int bottomSpacerHeight;
 
         if (extraHeight < mTotalSpacerIdealHeight) {
             // The spacers will be less than their ideal height, shrink them proportionally.
             topSpacerHeight =
                     Math.round(extraHeight * (TOP_SPACER_HEIGHT_DP / TOTAL_SPACER_HEIGHT_DP));
             middleSpacerHeight =
                     Math.round(extraHeight * (MIDDLE_SPACER_HEIGHT_DP / TOTAL_SPACER_HEIGHT_DP));
             bottomSpacerHeight = extraHeight - topSpacerHeight - middleSpacerHeight;
         } else {
             // Distribute remaining space evenly between the top and bottom spacers.
             extraHeight -= mTotalSpacerIdealHeight;
             topSpacerHeight = mTopSpacerIdealHeight + extraHeight / 2;
             middleSpacerHeight = mMiddleSpacerIdealHeight;
             bottomSpacerHeight = mBottomSpacerIdealHeight + extraHeight / 2;
         }
 
-        setMeasure(mTopSpacer, 0, topSpacerHeight);
-        setMeasure(mMiddleSpacer, 0, middleSpacerHeight);
-        setMeasure(mBottomSpacer, 0, bottomSpacerHeight);
+        measureExactly(mTopSpacer, 0, topSpacerHeight);
+        measureExactly(mMiddleSpacer, 0, middleSpacerHeight);
+        measureExactly(mBottomSpacer, 0, bottomSpacerHeight);
     }
 
-
     /**
-     * Convenience method to call |measure| on the given View with MeasureSpecs converted from the
+     * Convenience method to call measure() on the given View with MeasureSpecs converted from the
      * given dimensions (in pixels) with MeasureSpec.EXACTLY.
      */
-    private void setMeasure(View view, int widthPx, int heightPx) {
+    private static void measureExactly(View view, int widthPx, int heightPx) {
         view.measure(MeasureSpec.makeMeasureSpec(widthPx, MeasureSpec.EXACTLY),
                 MeasureSpec.makeMeasureSpec(heightPx, MeasureSpec.EXACTLY));
     }
 }