(Reland) Top-chrome slide: Fix and test intermediate sliding

Gesture scrolling starts before top-chrome starts
sliding. During that small period, the
`DoBrowserControlsShrinkRendererSize` bit should
remain unchanged.

This CL fixes this issue and adds a test to verify
the state of the browser while top-chrome sliding
is in progress.

BUG=884440, 867063, 891516
TEST=Added new test

Reviewed-on: https://chromium-review.googlesource.com/c/1249729Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: David Bokan <bokan@chromium.org>
Commit-Queue: Ahmed Fakhry <afakhry@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#595899}
Change-Id: I63f101175c1ec1052d6e0bb55bbe760fd7a8b369
Reviewed-on: https://chromium-review.googlesource.com/c/1260105
Cr-Commit-Position: refs/heads/master@{#596700}

chrome/browser/ui/views/frame/OWNERS

@@ -5,5 +5,6 @@ sky@chromium.org
 per-file immersive_mode_controller*=pkotwicz@chromium.org
 per-file *x11*=thomasanderson@chromium.org
 per-file desktop_linux_browser_frame_view*=thomasanderson@chromium.org
+per-file top_controls_slide_controller*=afakhry@chromium.org
 
 # COMPONENT: UI>Browser

chrome/browser/ui/views/frame/top_controls_slide_controller.h

@@ -52,6 +52,9 @@ class TopControlsSlideController {
   // changed state.
   virtual void SetTopControlsGestureScrollInProgress(bool in_progress) = 0;
 
+  // Returns true while gesture scrolls are in progress.
+  virtual bool IsTopControlsGestureScrollInProgress() const = 0;
+
  private:
   DISALLOW_COPY_AND_ASSIGN(TopControlsSlideController);
 };

chrome/browser/ui/views/frame/top_controls_slide_controller_chromeos.cc

@@ -163,9 +163,9 @@ class TopControlsSlideTabObserver : public content::WebContentsObserver {
   float shown_ratio() const { return shown_ratio_; }
   bool shrink_renderer_size() const { return shrink_renderer_size_; }
 
-  void SetShownRatio(float ratio, bool sliding_in_progress) {
+  void SetShownRatio(float ratio, bool sliding_or_scrolling_in_progress) {
     shown_ratio_ = ratio;
-    if (!sliding_in_progress)
+    if (!sliding_or_scrolling_in_progress)
       UpdateDoBrowserControlsShrinkRendererSize();
   }
 
@@ -248,8 +248,8 @@ class TopControlsSlideTabObserver : public content::WebContentsObserver {
 
   // Indicates whether the renderer's viewport size should be shrunk by the
   // height of the browser's top controls. This value should only be updated at
-  // the end of sliding, and should never change while sliding is in progress.
-  // https://crbug.com/885223.
+  // the end of sliding, and should never change while sliding or scrolling are
+  // in progress. https://crbug.com/885223.
   bool shrink_renderer_size_ = true;
 
   DISALLOW_COPY_AND_ASSIGN(TopControlsSlideTabObserver);
@@ -303,7 +303,22 @@ void TopControlsSlideControllerChromeOS::SetShownRatio(
   // Make sure the value tracked per tab is always updated even when sliding is
   // disabled, so that we're always synchronized with the renderer.
   DCHECK(observed_tabs_.count(contents));
-  observed_tabs_[contents]->SetShownRatio(ratio, is_sliding_in_progress_);
+
+  // Note that there are two small windows of intervals between:
+  // 1- When |is_gesture_scrolling_in_progress_| is set to true (i.e. received
+  //    ET_GESTURE_SCROLL_BEGIN) and when |is_sliding_in_progress_| is set to
+  //    true (i.e. top-chrome actually starts moving), and
+  // 2- When |is_gesture_scrolling_in_progress_| is set to false (i.e.
+  //    ET_GESTURE_SCROLL_END was received) and when |is_sliding_in_progress_|
+  //    is set to false (i.e. top-chrome stopped moving) which can happen as the
+  //    renderer continues to animate top-chrome towards fully-shown or
+  //    fully-hidden after the user had lifted their fingers while the
+  //    shown_ratio is still a fractional value.
+  // Even during those two small windows, the
+  // `DoBrowserControlsShrinkRendererSize` bit should remain unchanged from its
+  // current value until sliding reaches a steady state.
+  observed_tabs_[contents]->SetShownRatio(
+      ratio, is_gesture_scrolling_in_progress_ || is_sliding_in_progress_);
 
   if (!IsEnabled()) {
     // However, if sliding is disabled, we don't update |shown_ratio_|, which is
@@ -369,6 +384,11 @@ void TopControlsSlideControllerChromeOS::SetTopControlsGestureScrollInProgress(
   Refresh();
 }
 
+bool TopControlsSlideControllerChromeOS::IsTopControlsGestureScrollInProgress()
+    const {
+  return is_gesture_scrolling_in_progress_;
+}
+
 void TopControlsSlideControllerChromeOS::OnTabletModeToggled(
     bool tablet_mode_enabled) {
   OnEnabledStateChanged(tablet_mode_enabled && !browser_view_->IsFullscreen());

chrome/browser/ui/views/frame/top_controls_slide_controller_chromeos.h

@@ -51,6 +51,7 @@ class TopControlsSlideControllerChromeOS
   bool DoBrowserControlsShrinkRendererSize(
       const content::WebContents* contents) const override;
   void SetTopControlsGestureScrollInProgress(bool in_progress) override;
+  bool IsTopControlsGestureScrollInProgress() const override;
 
   // TabletModeClientObserver:
   void OnTabletModeToggled(bool tablet_mode_enabled) override;