Reland "Consistent touchpad pinch behaviour for app windows and webviews"

This is a reland of be51aadb

Original change's description:
> Consistent touchpad pinch behaviour for app windows and webviews
> 
> Currently, app windows (possibly containing webviews):
> 1) suppress all pinch events which also suppresses the
>    synthetic wheel event, but not touchscreen touch events, and
> 2) allow "smart zoom" on Mac which can change the page scale even
>    though other means of changing the page scale are suppressed.
> 
> As a result of (1), if we have, say, google maps in a webview, a
> user can pinch zoom with a touchscreen, but not with a touchpad.
> 
> We now suppress gesture events to app windows based on whether they
> cause a scale change. So now touchscreen and touchpad pinching are
> consistent since the page has access to the events so that it may
> implement custom pinch zoom behaviour, but unhandled events still
> do not result in a scale change for the app window. Also, smart
> zoom is suppressed to be consistent with other touchpad pinching.
> 
> Bug: 725970, 874132
> Change-Id: I03dd2048002d69dc7c8a822fc727140c67d64706
> Reviewed-on: https://chromium-review.googlesource.com/1174933
> Reviewed-by: Ben Wells <benwells@chromium.org>
> Reviewed-by: James MacLean <wjmaclean@chromium.org>
> Reviewed-by: Ehsan Karamad <ekaramad@chromium.org>
> Commit-Queue: Kevin McNee <mcnee@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#585489}

Bug: 725970, 874132
Change-Id: I23420821c1166f7b641faf672798ddac0e928ad9
Reviewed-on: https://chromium-review.googlesource.com/1187345Reviewed-by: Ehsan Karamad <ekaramad@chromium.org>
Reviewed-by: James MacLean <wjmaclean@chromium.org>
Reviewed-by: Ben Wells <benwells@chromium.org>
Commit-Queue: Kevin McNee <mcnee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#585856}

chrome/browser/apps/guest_view/web_view_browsertest.cc

@@ -4430,3 +4430,21 @@ IN_PROC_BROWSER_TEST_F(WebViewTest, AutoResizeMessages) {
       embedder->GetRenderWidgetHostView()->GetRenderWidgetHost()->GetProcess(),
       guest->GetRenderWidgetHostView()->GetRenderWidgetHost()));
 }
+
+// Test that a guest sees the synthetic wheel events of a touchpad pinch.
+IN_PROC_BROWSER_TEST_F(WebViewTest, TouchpadPinchSyntheticWheelEvents) {
+  ASSERT_TRUE(StartEmbeddedTestServer());
+  LoadAppWithGuest("web_view/touchpad_pinch");
+  content::WebContents* guest_contents = GetGuestWebContents();
+
+  ExtensionTestMessageListener synthetic_wheel_listener("Seen wheel event",
+                                                        false);
+
+  const gfx::Rect contents_rect = guest_contents->GetContainerBounds();
+  const gfx::Point pinch_position(contents_rect.width() / 2,
+                                  contents_rect.height() / 2);
+  content::SimulateGesturePinchSequence(guest_contents, pinch_position, 1.23,
+                                        blink::kWebGestureDeviceTouchpad);
+
+  ASSERT_TRUE(synthetic_wheel_listener.WaitUntilSatisfied());
+}

chrome/browser/apps/platform_apps/app_browsertest.cc

@@ -1400,4 +1400,27 @@ IN_PROC_BROWSER_TEST_F(PlatformAppBrowserTest, NewWindowAboutBlank) {
   ASSERT_TRUE(RunPlatformAppTest("platform_apps/new_window_about_blank"));
 }
 
+// Test that an app window sees the synthetic wheel events of a touchpad pinch.
+// While the app window itself does not scale in response to a pinch, we
+// still offer the synthetic wheels for pages that want to implement custom
+// pinch zoom behaviour.
+IN_PROC_BROWSER_TEST_F(PlatformAppBrowserTest,
+                       TouchpadPinchSyntheticWheelEvents) {
+  LoadAndLaunchPlatformApp("touchpad_pinch", "Launched");
+
+  WebContents* web_contents = GetFirstAppWindowWebContents();
+  ASSERT_TRUE(web_contents);
+
+  ExtensionTestMessageListener synthetic_wheel_listener("Seen wheel event",
+                                                        false);
+
+  const gfx::Rect contents_rect = web_contents->GetContainerBounds();
+  const gfx::Point pinch_position(contents_rect.width() / 2,
+                                  contents_rect.height() / 2);
+  content::SimulateGesturePinchSequence(web_contents, pinch_position, 1.23,
+                                        blink::kWebGestureDeviceTouchpad);
+
+  ASSERT_TRUE(synthetic_wheel_listener.WaitUntilSatisfied());
+}
+
 }  // namespace extensions

chrome/test/data/extensions/platform_apps/touchpad_pinch/background.js

+// Copyright 2018 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.
+
+chrome.app.runtime.onLaunched.addListener(function() {
+  chrome.app.window.create('window.html');
+});

chrome/test/data/extensions/platform_apps/touchpad_pinch/manifest.json

+{
+  "name": "Touchpad pinch synthetic wheel event",
+  "version": "1",
+  "manifest_version": 2,
+  "app": {
+    "background": {
+      "scripts": ["background.js"]
+    }
+  }
+}

chrome/test/data/extensions/platform_apps/touchpad_pinch/window.html

+<!--
+ * Copyright (c) 2018 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.
+-->
+<html>
+<head>
+  <style>
+    html,body {
+     height: 100%;
+    }
+  </style>
+</head>
+<body>
+  <p>Hello.</p>
+  <script src="window.js"></script>
+</body>
+</html>

chrome/test/data/extensions/platform_apps/touchpad_pinch/window.js

+// Copyright 2018 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.
+
+window.onload = () => {
+  document.body.addEventListener('wheel', (e) => {
+    chrome.test.sendMessage('Seen wheel event');
+  });
+
+  // We need to wait for the compositor thread to be made aware of the wheel
+  // listener before sending the pinch event sequence.
+  window.requestAnimationFrame(() => {
+    window.requestAnimationFrame(() => {
+      chrome.test.sendMessage('Launched');
+    });
+  });
+};

chrome/test/data/extensions/platform_apps/web_view/touchpad_pinch/embedder.html

+<!--
+ * Copyright (c) 2018 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.
+-->
+<html>
+<body>
+<script src="embedder.js"></script>
+</body>
+</html>

chrome/test/data/extensions/platform_apps/web_view/touchpad_pinch/embedder.js

+// Copyright 2018 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.
+
+window.onload = () => {
+  chrome.test.getConfig(function(config) {
+    var guestURL = 'http://localhost:' + config.testServer.port +
+        '/extensions/platform_apps/web_view/touchpad_pinch/guest.html';
+    var webview = document.createElement('webview');
+    webview.src = guestURL;
+    webview.addEventListener('loadstop', () => {
+      webview.contentWindow.postMessage({}, '*');
+    });
+    document.body.appendChild(webview);
+  });
+};
+
+window.addEventListener('message', (e) => {
+  chrome.test.sendMessage(e.data);
+});

chrome/test/data/extensions/platform_apps/web_view/touchpad_pinch/guest.html

+<!--
+ * Copyright (c) 2018 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.
+-->
+<html>
+<head>
+  <style>
+    html,body {
+     height: 100%;
+    }
+  </style>
+</head>
+<body>
+  <p>Hello.</p>
+  <script src="guest.js"></script>
+</body>
+</html>

chrome/test/data/extensions/platform_apps/web_view/touchpad_pinch/guest.js

+// Copyright 2018 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.
+
+var parentWindow = null;
+
+window.onload = () => {
+  document.body.addEventListener('wheel', (e) => {
+    parentWindow.postMessage('Seen wheel event', '*');
+  });
+};
+
+window.addEventListener('message', (e) => {
+  parentWindow = e.source;
+
+  // We need to wait for the compositor thread to be made aware of the wheel
+  // listener before sending the pinch event sequence.
+  window.requestAnimationFrame(() => {
+    window.requestAnimationFrame(() => {
+      parentWindow.postMessage('WebViewTest.LAUNCHED', '*');
+    });
+  });
+});

chrome/test/data/extensions/platform_apps/web_view/touchpad_pinch/manifest.json

+{
+  "name": "<webview> Touchpad pinch synthetic wheel event",
+  "version": "1",
+  "manifest_version": 2,
+  "permissions": [
+    "webview"
+  ],
+  "app": {
+    "background": {
+      "scripts": ["test.js"]
+    }
+  }
+}

chrome/test/data/extensions/platform_apps/web_view/touchpad_pinch/test.js

+// Copyright 2018 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.
+
+chrome.app.runtime.onLaunched.addListener(function() {
+  chrome.app.window.create('embedder.html');
+});

components/guest_view/browser/guest_view_base.cc

@@ -683,7 +683,11 @@ bool GuestViewBase::ShouldFocusPageAfterCrash() {
 
 bool GuestViewBase::PreHandleGestureEvent(WebContents* source,
                                           const blink::WebGestureEvent& event) {
-  return blink::WebInputEvent::IsPinchGestureEventType(event.GetType());
+  // Pinch events which cause a scale change should not be routed to a guest.
+  // We still allow synthetic wheel events for touchpad pinch to go to the page.
+  DCHECK(!blink::WebInputEvent::IsPinchGestureEventType(event.GetType()) ||
+         event.NeedsWheelEvent());
+  return false;
 }
 
 void GuestViewBase::UpdatePreferredSize(WebContents* target_web_contents,

extensions/browser/app_window/app_web_contents_helper.cc

@@ -32,8 +32,18 @@ AppWebContentsHelper::AppWebContentsHelper(
 // static
 bool AppWebContentsHelper::ShouldSuppressGestureEvent(
     const blink::WebGestureEvent& event) {
+  // Disable "smart zoom" (double-tap with two fingers on Mac trackpad).
+  if (event.GetType() == blink::WebInputEvent::kGestureDoubleTap)
+    return true;
+
   // Disable pinch zooming in app windows.
-  return blink::WebInputEvent::IsPinchGestureEventType(event.GetType());
+  if (blink::WebInputEvent::IsPinchGestureEventType(event.GetType())) {
+    // Only suppress pinch events that cause a scale change. We still
+    // allow synthetic wheel events for touchpad pinch to go to the page.
+    return !event.NeedsWheelEvent();
+  }
+
+  return false;
 }
 
 content::WebContents* AppWebContentsHelper::OpenURLFromTab(