Disable swipe down to enter the tab switcher in Chrome Home.

BUG=

Review-Url: https://codereview.chromium.org/2755823004
Cr-Commit-Position: refs/heads/master@{#457836}

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

@@ -179,7 +179,7 @@ public class LayoutManagerChrome
         mOverviewModeObservers = new ObserverList<OverviewModeObserver>();
 
         // Build Event Filter Handlers
-        mToolbarSwipeHandler = new ToolbarSwipeHandler(this);
+        mToolbarSwipeHandler = createToolbarSwipeHandler(this);
 
         // Build Event Filters
         mBlackHoleEventFilter = new BlackHoleEventFilter(context, this);
@@ -685,11 +685,13 @@ public class LayoutManagerChrome
                 return false;
             }
 
-            boolean isAccessibility =
-                    DeviceClassManager.isAccessibilityModeEnabled(mHost.getContext());
-            return direction == ScrollDirection.LEFT || direction == ScrollDirection.RIGHT
-                    || (direction == ScrollDirection.DOWN && mOverviewLayout != null
-                               && !isAccessibility);
+            if (direction == ScrollDirection.DOWN) {
+                boolean isAccessibility =
+                        DeviceClassManager.isAccessibilityModeEnabled(mHost.getContext());
+                return mOverviewLayout != null && !isAccessibility;
+            }
+
+            return direction == ScrollDirection.LEFT || direction == ScrollDirection.RIGHT;
         }
     }
 

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

@@ -8,6 +8,7 @@ import android.content.Context;
 import android.view.ViewGroup;
 
 import org.chromium.chrome.browser.compositor.layouts.content.TabContentManager;
+import org.chromium.chrome.browser.compositor.layouts.eventfilter.EdgeSwipeEventFilter.ScrollDirection;
 import org.chromium.chrome.browser.compositor.layouts.phone.SimpleAnimationLayout;
 import org.chromium.chrome.browser.compositor.overlays.SceneOverlay;
 import org.chromium.chrome.browser.contextualsearch.ContextualSearchManagementDelegate;
@@ -17,6 +18,7 @@ import org.chromium.chrome.browser.tabmodel.TabCreatorManager;
 import org.chromium.chrome.browser.tabmodel.TabModel.TabLaunchType;
 import org.chromium.chrome.browser.tabmodel.TabModelSelector;
 import org.chromium.chrome.browser.tabmodel.TabModelUtils;
+import org.chromium.chrome.browser.util.FeatureUtilities;
 import org.chromium.ui.resources.dynamics.DynamicResourceLoader;
 
 /**
@@ -47,6 +49,11 @@ public class LayoutManagerChromePhone extends LayoutManagerChrome {
         mToolbarSwipeLayout.setMovesToolbar(true);
     }
 
+    @Override
+    protected ToolbarSwipeHandler createToolbarSwipeHandler(LayoutProvider provider) {
+        return new PhoneToolbarSwipeHandler(provider);
+    }
+
     @Override
     public void init(TabModelSelector selector, TabCreatorManager creator,
             TabContentManager content, ViewGroup androidContentContainer,
@@ -150,4 +157,19 @@ public class LayoutManagerChromePhone extends LayoutManagerChrome {
         mTitleCache.remove(id);
         super.releaseTabLayout(id);
     }
+
+    private class PhoneToolbarSwipeHandler extends ToolbarSwipeHandler {
+        public PhoneToolbarSwipeHandler(LayoutProvider provider) {
+            super(provider);
+        }
+
+        @Override
+        public boolean isSwipeEnabled(ScrollDirection direction) {
+            if (direction == ScrollDirection.DOWN && FeatureUtilities.isChromeHomeEnabled()) {
+                return false;
+            }
+
+            return super.isSwipeEnabled(direction);
+        }
+    }
 }