Initial hookup of CSS prefers-reduced-motion for Mac/Win

For now, the hookup is static; changing the OS level settings will not
cause the settings to be recalculated.

Test: Manually verified functional on Mac and Windows.
Bug: 722548
Change-Id: Iccb601a28d26a7ac659677041ce637bdd19e7db3
Reviewed-on: https://chromium-review.googlesource.com/c/1417754
Commit-Queue: Stephen McGruer <smcgruer@chromium.org>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Ian Vollick <vollick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#625249}

content/browser/renderer_host/render_view_host_impl.cc

@@ -532,6 +532,8 @@ const WebPreferences RenderViewHostImpl::ComputeWebPreferences() {
       (!command_line.HasSwitch(switches::kDisableSmoothScrolling) &&
       gfx::Animation::ScrollAnimationsEnabledBySystem());
 
+  prefs.prefers_reduced_motion = gfx::Animation::PrefersReducedMotion();
+
   if (ChildProcessSecurityPolicyImpl::GetInstance()->HasWebUIBindings(
           GetProcess()->GetID())) {
     prefs.loads_images_automatically = true;

content/public/common/common_param_traits_macros.h

@@ -165,6 +165,7 @@ IPC_STRUCT_TRAITS_BEGIN(content::WebPreferences)
   IPC_STRUCT_TRAITS_MEMBER(strictly_block_blockable_mixed_content)
   IPC_STRUCT_TRAITS_MEMBER(block_mixed_plugin_content)
   IPC_STRUCT_TRAITS_MEMBER(enable_scroll_animator)
+  IPC_STRUCT_TRAITS_MEMBER(prefers_reduced_motion)
   IPC_STRUCT_TRAITS_MEMBER(password_echo_enabled)
   IPC_STRUCT_TRAITS_MEMBER(should_clear_document_background)
   IPC_STRUCT_TRAITS_MEMBER(touch_event_feature_detection_enabled)

content/public/common/web_preferences.cc

@@ -121,6 +121,7 @@ WebPreferences::WebPreferences()
       should_print_backgrounds(false),
       should_clear_document_background(true),
       enable_scroll_animator(false),
+      prefers_reduced_motion(false),
       touch_event_feature_detection_enabled(false),
       touch_adjustment_enabled(true),
       pointer_events_max_touch_points(0),

content/public/common/web_preferences.h

@@ -161,6 +161,7 @@ struct CONTENT_EXPORT WebPreferences {
   bool should_print_backgrounds;
   bool should_clear_document_background;
   bool enable_scroll_animator;
+  bool prefers_reduced_motion;
   bool touch_event_feature_detection_enabled;
   bool touch_adjustment_enabled;
   int pointer_events_max_touch_points;

content/renderer/render_view_impl.cc

@@ -757,6 +757,7 @@ void RenderView::ApplyWebPreferences(const WebPreferences& prefs,
   settings->SetShouldClearDocumentBackground(
       prefs.should_clear_document_background);
   settings->SetEnableScrollAnimator(prefs.enable_scroll_animator);
+  settings->SetPrefersReducedMotion(prefs.prefers_reduced_motion);
 
   WebRuntimeFeatures::EnableTouchEventFeatureDetection(
       prefs.touch_event_feature_detection_enabled);

third_party/blink/public/web/web_settings.h

@@ -152,6 +152,7 @@ class WebSettings {
   virtual void SetDownloadableBinaryFontsEnabled(bool) = 0;
   virtual void SetEditingBehavior(EditingBehavior) = 0;
   virtual void SetEnableScrollAnimator(bool) = 0;
+  virtual void SetPrefersReducedMotion(bool) = 0;
   virtual void SetEnableTouchAdjustment(bool) = 0;
   virtual void SetSmoothScrollForFindEnabled(bool) = 0;
   virtual void SetWebGL1Enabled(bool) = 0;

third_party/blink/renderer/core/exported/web_settings_impl.cc

@@ -564,6 +564,10 @@ void WebSettingsImpl::SetEnableScrollAnimator(bool enabled) {
   settings_->SetScrollAnimatorEnabled(enabled);
 }
 
+void WebSettingsImpl::SetPrefersReducedMotion(bool enabled) {
+  settings_->SetPrefersReducedMotion(enabled);
+}
+
 void WebSettingsImpl::SetEnableTouchAdjustment(bool enabled) {
   settings_->SetTouchAdjustmentEnabled(enabled);
 }

third_party/blink/renderer/core/exported/web_settings_impl.h

@@ -82,6 +82,7 @@ class CORE_EXPORT WebSettingsImpl final : public WebSettings {
   void SetDownloadableBinaryFontsEnabled(bool) override;
   void SetEditingBehavior(EditingBehavior) override;
   void SetEnableScrollAnimator(bool) override;
+  void SetPrefersReducedMotion(bool) override;
   void SetEnableTouchAdjustment(bool) override;
   void SetWebGL1Enabled(bool) override;
   void SetWebGL2Enabled(bool) override;

ui/gfx/animation/animation.cc

@@ -113,6 +113,12 @@ bool Animation::ScrollAnimationsEnabledBySystem() {
   // Defined in platform specific files for Windows and OSX.
   return true;
 }
+
+bool Animation::PrefersReducedMotion() {
+  // By default, we assume that animations are enabled, to avoid impacting the
+  // experience for users on systems that don't have APIs for reduced motion.
+  return false;
+}
 #endif
 
 bool Animation::ShouldSendCanceledFromStop() {

ui/gfx/animation/animation.h

@@ -79,6 +79,10 @@ class ANIMATION_EXPORT Animation : public AnimationContainerElement {
   // process.
   static bool ScrollAnimationsEnabledBySystem();
 
+  // Determines whether the user desires reduced motion based on platform APIs.
+  // Should only be called from the browser process.
+  static bool PrefersReducedMotion();
+
  protected:
   // Invoked from Start to allow subclasses to prepare for the animation.
   virtual void AnimationStarted() {}

ui/gfx/animation/animation_mac.mm

@@ -4,11 +4,16 @@
 
 #include "ui/gfx/animation/animation.h"
 
-#import <Foundation/Foundation.h>
+#import <Cocoa/Cocoa.h>
 
 #include "base/mac/mac_util.h"
 #include "base/message_loop/message_loop.h"
 
+// Only available since 10.12.
+@interface NSWorkspace (AvailableSinceSierra)
+@property(readonly) BOOL accessibilityDisplayShouldReduceMotion;
+@end
+
 namespace gfx {
 
 // static
@@ -27,4 +32,22 @@ bool Animation::ScrollAnimationsEnabledBySystem() {
   return enabled;
 }
 
+// static
+bool Animation::PrefersReducedMotion() {
+  // Because of sandboxing, OS settings should only be queried from the browser
+  // process.
+  DCHECK(base::MessageLoopCurrentForUI::IsSet() ||
+         base::MessageLoopCurrentForIO::IsSet());
+
+  // We default to assuming that animations are enabled, to avoid impacting the
+  // experience for users on pre-10.12 systems.
+  bool prefers_reduced_motion = false;
+  SEL sel = @selector(accessibilityDisplayShouldReduceMotion);
+  if ([[NSWorkspace sharedWorkspace] respondsToSelector:sel]) {
+    prefers_reduced_motion =
+        [[NSWorkspace sharedWorkspace] accessibilityDisplayShouldReduceMotion];
+  }
+  return prefers_reduced_motion;
+}
+
 } // namespace gfx

ui/gfx/animation/animation_win.cc

@@ -23,4 +23,13 @@ bool Animation::ScrollAnimationsEnabledBySystem() {
   return ShouldRenderRichAnimation();
 }
 
+// static
+bool Animation::PrefersReducedMotion() {
+  // We default to assuming that animations are enabled, to avoid impacting the
+  // experience for users on systems that don't have SPI_GETCLIENTAREAANIMATION.
+  BOOL win_anim_enabled = true;
+  SystemParametersInfo(SPI_GETCLIENTAREAANIMATION, 0, &win_anim_enabled, 0);
+  return !win_anim_enabled;
+}
+
 } // namespace gfx