When possible, draw the toolbar shadow with the compositor

chrome/android/java/src/org/chromium/chrome/browser/compositor/scene_layer/ToolbarSceneLayer.java

Index: chrome/android/java/src/org/chromium/chrome/browser/compositor/scene_layer/ToolbarSceneLayer.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/compositor/scene_layer/ToolbarSceneLayer.java b/chrome/android/java/src/org/chromium/chrome/browser/compositor/scene_layer/ToolbarSceneLayer.java
index 148c8b68598da141ba9196b36af5e0febbede90c..4c1e4665618ce554c8fdc4dcba93d5ff90d5143b 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/compositor/scene_layer/ToolbarSceneLayer.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/compositor/scene_layer/ToolbarSceneLayer.java
@@ -17,6 +17,8 @@ import org.chromium.chrome.browser.compositor.layouts.eventfilter.EventFilter;
 import org.chromium.chrome.browser.compositor.overlays.SceneOverlay;
 import org.chromium.chrome.browser.device.DeviceClassManager;
 import org.chromium.chrome.browser.fullscreen.ChromeFullscreenManager;
+import org.chromium.chrome.browser.tab.Tab;
+import org.chromium.chrome.browser.tabmodel.TabModelSelector;
 import org.chromium.chrome.browser.widget.ClipDrawableProgressBar.DrawingInfo;
 import org.chromium.chrome.browser.widget.ControlContainer;
 import org.chromium.ui.base.DeviceFormFactor;
@@ -45,6 +47,9 @@ public class ToolbarSceneLayer extends SceneOverlayLayer implements SceneOverlay
     /** A LayoutRenderHost for accessing drawing information about the toolbar. */
     private LayoutRenderHost mRenderHost;
 
+    /** Used to get information about the current selected tab. */
+    private TabModelSelector mTabModelSelector;
+
     /**
      * @param context An Android context to use.
      * @param provider A LayoutProvider for accessing the current layout.
@@ -58,6 +63,13 @@ public class ToolbarSceneLayer extends SceneOverlayLayer implements SceneOverlay
     }
 
     /**
+     * @param tabModelSelector A TabModelSelector so this class can know about the current tab.
+     */
+    public void setTabModelSelector(TabModelSelector tabModelSelector) {
+        mTabModelSelector = tabModelSelector;
+    }
+
+    /**
      * Update the toolbar and progress bar layers.
      *
      * @param topControlsBackgroundColor The background color of the top controls.
@@ -94,9 +106,17 @@ public class ToolbarSceneLayer extends SceneOverlayLayer implements SceneOverlay
             useTexture = false;
         }
 
+        Tab currentTab = null;
+        if (mTabModelSelector != null) currentTab = mTabModelSelector.getCurrentTab();
+
+        boolean needsToolbarShadow = true;
+        if (currentTab != null && currentTab.getNativePage() != null) {
+            needsToolbarShadow &= currentTab.getNativePage().needsToolbarShadow();
+        }
+
         nativeUpdateToolbarLayer(mNativePtr, resourceManager, R.id.control_container,
-                topControlsBackgroundColor, R.drawable.textbox, topControlsUrlBarAlpha, offset,
-                useTexture, forceHideAndroidTopControls);
+                R.drawable.toolbar_shadow, topControlsBackgroundColor, R.drawable.textbox,
+                topControlsUrlBarAlpha, offset, useTexture, needsToolbarShadow);
 
         if (mProgressBarDrawingInfo == null) return;
         nativeUpdateProgressBar(mNativePtr,
@@ -234,6 +254,7 @@ public class ToolbarSceneLayer extends SceneOverlayLayer implements SceneOverlay
             long nativeToolbarSceneLayer,
             ResourceManager resourceManager,
             int resourceId,
+            int shadowResourceId,
             int toolbarBackgroundColor,
             int urlBarResourceId,
             float urlBarAlpha,