When possible, draw the toolbar shadow with the compositor

chrome/android/java/src/org/chromium/chrome/browser/toolbar/ToolbarPhone.java

Index: chrome/android/java/src/org/chromium/chrome/browser/toolbar/ToolbarPhone.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/toolbar/ToolbarPhone.java b/chrome/android/java/src/org/chromium/chrome/browser/toolbar/ToolbarPhone.java
index 1ac2662a235c7496a27b722ece61466d6f738d17..735bbee18c4b5a56bdc301f379fdf34c8c115ba0 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/toolbar/ToolbarPhone.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/toolbar/ToolbarPhone.java
@@ -122,6 +122,7 @@ public class ToolbarPhone extends ToolbarLayout
     private TextView mUrlBar;
     private View mUrlActionContainer;
     private ImageView mToolbarShadow;
+    private boolean mUrlHasFocus;
 
     private final int mProgressBackBackgroundColorWhite;
 
@@ -132,6 +133,7 @@ public class ToolbarPhone extends ToolbarLayout
     private final Set<View> mBrowsingModeViews = new HashSet<>();
     @ViewDebug.ExportedProperty(category = "chrome")
     private int mTabSwitcherState;
+    private boolean mIsCompositorReady;
 
     // This determines whether or not the toolbar draws as expected (false) or whether it always
     // draws as if it's showing the non-tabswitcher, non-animating toolbar. This is used in grabbing
@@ -173,6 +175,8 @@ public class ToolbarPhone extends ToolbarLayout
     @ViewDebug.ExportedProperty(category = "chrome")
     private float mUrlFocusChangePercent;
 
+    private float mToolbarShadowAlpha;
+
     /**
      * The degree to which the omnibox has expanded to full width, either because it is getting
      * focused or the NTP search box is being scrolled up. Note that in the latter case, the actual
@@ -265,6 +269,7 @@ public class ToolbarPhone extends ToolbarLayout
 
     private NewTabPage mVisibleNewTabPage;
     private float mPreTextureCaptureAlpha = 1f;
+    private int mPreTextureCaptureVisibility;
     private boolean mIsOverlayTabStackDrawableLight;
 
     // The following are some properties used during animation.  We use explicit property classes
@@ -280,6 +285,7 @@ public class ToolbarPhone extends ToolbarLayout
         @Override
         public void set(ToolbarPhone object, Float value) {
             setUrlFocusChangePercent(value);
+            setToolbarShadowAlpha(value);
         }
     };
 
@@ -877,12 +883,12 @@ public class ToolbarPhone extends ToolbarLayout
     private void resetNtpAnimationValues() {
         mLocationBarBackgroundNtpOffset.setEmpty();
         mLocationBar.setTranslationY(0);
+
         if (!mUrlFocusChangeInProgress) {
             mToolbarButtonsContainer.setTranslationY(0);
             mReturnButton.setTranslationY(0);
             mHomeButton.setTranslationY(0);
         }
-        mToolbarShadow.setAlpha(1f);
         mLocationBar.setAlpha(1);
         mForceDrawLocationBarBackground = false;
         mLocationBarBackgroundAlpha = 255;
@@ -905,7 +911,6 @@ public class ToolbarPhone extends ToolbarLayout
         if (mTabSwitcherState == TAB_SWITCHER || mTabSwitcherState == ENTERING_TAB_SWITCHER) return;
 
         setAncestorsShouldClipChildren(mUrlExpansionPercent == 0f);
-        mToolbarShadow.setAlpha(0f);
 
         NewTabPage ntp = getToolbarDataProvider().getNewTabPageForCurrentTab();
         ntp.getSearchBoxBounds(mNtpSearchBoxBounds, mNtpSearchBoxTranslation);
@@ -1437,10 +1442,12 @@ public class ToolbarPhone extends ToolbarLayout
         assert mTextureCaptureMode != textureMode;
         mTextureCaptureMode = textureMode;
         if (mTextureCaptureMode) {
-            mToolbarShadow.setVisibility(VISIBLE);
+            mPreTextureCaptureVisibility = mToolbarShadow.getVisibility();
+            mToolbarShadow.setVisibility(INVISIBLE);
             mPreTextureCaptureAlpha = getAlpha();
             setAlpha(1);
         } else {
+            mToolbarShadow.setVisibility(mPreTextureCaptureVisibility);
             setAlpha(mPreTextureCaptureAlpha);
             updateShadowVisibility();
             mPreTextureCaptureAlpha = 1f;
@@ -1763,6 +1770,7 @@ public class ToolbarPhone extends ToolbarLayout
         triggerUrlFocusAnimation(hasFocus);
 
         TransitionDrawable shadowDrawable = (TransitionDrawable) mToolbarShadow.getDrawable();
+
         if (hasFocus) {
             dismissTabSwitcherCallout();
             shadowDrawable.startTransition(URL_FOCUS_CHANGE_ANIMATION_DURATION_MS);
@@ -1809,6 +1817,7 @@ public class ToolbarPhone extends ToolbarLayout
             public void onAnimationEnd(Animator animation) {
                 if (mCanceled) return;
 
+                mUrlHasFocus = hasFocus;
                 if (!hasFocus) {
                     mDisableLocationBarRelayout = false;
                     mLayoutLocationBarInFocusedMode = false;
@@ -1816,6 +1825,7 @@ public class ToolbarPhone extends ToolbarLayout
                 }
                 mLocationBar.finishUrlFocusChange(hasFocus);
                 mUrlFocusChangeInProgress = false;
+                updateShadowVisibility();
             }
         });
         mUrlFocusLayoutAnimator.start();
@@ -1882,6 +1892,8 @@ public class ToolbarPhone extends ToolbarLayout
             mHasCheckedIfTabSwitcherCalloutIsNecessary = true;
             showTabSwitcherCalloutIfNecessary();
         }
+
+        updateShadowVisibility();
     }
 
     private static boolean isVisualStateValidForBrandColorTransition(VisualState state) {
@@ -1991,13 +2003,54 @@ public class ToolbarPhone extends ToolbarLayout
         return ntp != null && ntp.isLocationBarShownInNTP();
     }
 
+    /**
+     * @return True if the Android version of the toolbar shadow is needed.
+     */
+    private boolean needsAndroidToolbarShadow() {
+        // Reasons to draw the Android toolbar shadow:
+        // 1. Web page is using a native view except in the case of the NTP.
+        // 2. Omnibox is focused and there are suggestions under it.
+        if (!mIsCompositorReady || getToolbarDataProvider() == null
+                || getToolbarDataProvider().getTab() == null) {
+            return true;
+        }
+        Tab tab = getToolbarDataProvider().getTab();
+
+        // If the shadow is not needed, this is definitely the NTP. There are other shadows that
+        // will show in place of the normal toolbar shadow.
+        if (tab.getNativePage() != null && !tab.getNativePage().needsToolbarShadow()) return false;
+
+        // Check if the current tab uses a native android View instead of a WebContents.
+        boolean usesNativeView = tab.isNativePage() || tab.isShowingSadTab();
+
+        return mTabSwitcherState == STATIC_TAB && (mUrlHasFocus || usesNativeView);
+    }
+
     private void updateShadowVisibility() {
-        boolean shouldDrawShadow = mTabSwitcherState == STATIC_TAB;
-        int shadowVisibility = shouldDrawShadow ? View.VISIBLE : View.INVISIBLE;
+        if (needsAndroidToolbarShadow()) {
+            mToolbarShadow.setAlpha(1.0f);
+        } else {
+            mToolbarShadow.setAlpha(0.0f);
+        }
+    }
 
-        if (mToolbarShadow.getVisibility() != shadowVisibility) {
-            mToolbarShadow.setVisibility(shadowVisibility);
+    /**
+     * Set the toolbar shadow's alpha during animation.
+     * @param alpha The alpha that the toolbar shadow should have.
+     */
+    private void setToolbarShadowAlpha(float value) {
+        boolean isNativePage = false;
+        if (getToolbarDataProvider() != null && getToolbarDataProvider().getTab() != null) {
+            isNativePage = getToolbarDataProvider().getTab().isNativePage();
         }
+
+        // If the toolbar shadow is always supposed be showing, don't fade it. Check if the page
+        // is native because the shadow might be showing becuase of the omnibox.
+        if (needsAndroidToolbarShadow() && isNativePage) {
+            mToolbarShadow.setAlpha(1.0f);
+            return;
+        }
+        mToolbarShadow.setAlpha(Math.min(value, 1.0f));
     }
 
     private VisualState computeVisualState(boolean isInTabSwitcherMode) {
@@ -2268,5 +2321,12 @@ public class ToolbarPhone extends ToolbarLayout
                             mFullscreenCalloutToken);
         }
     }
+
+    @Override
+    public void onFirstCompositorFrame() {
+        if (mIsCompositorReady) return;
+        mIsCompositorReady = true;
+        updateShadowVisibility();
+    }
 }