[Fullscreen Exit] Implement the experiment flag as a base::Feature

We're about to launch the fullscreen exit UI, starting at 100% for Dev and
Canary. Currently the flag for fullscreen exit UI is implemented as a
command line switch, which can't be used with Finch experiment. This CL
makes the flag base::Feature so that it can be controlled by experiment.

Bug: 829606
Change-Id: I955439a4cf6cdd6196fa6d9d42faaebabbc373b0
Reviewed-on: https://chromium-review.googlesource.com/1008724
Commit-Queue: Yuwei Huang <yuweih@chromium.org>
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Cr-Commit-Position: refs/heads/master@{#550086}

chrome/browser/about_flags.cc

@@ -3336,7 +3336,7 @@ const FeatureEntry kFeatureEntries[] = {
      flag_descriptions::kExperimentalFullscreenExitUIName,
      flag_descriptions::kExperimentalFullscreenExitUIDescription,
      kOsWin | kOsLinux | kOsCrOS,
-     SINGLE_VALUE_TYPE(switches::kEnableExperimentalFullscreenExitUI)},
+     FEATURE_VALUE_TYPE(features::kFullscreenExitUI)},
 #endif  // defined(TOOLKIT_VIEWS)
 
     {"network-service", flag_descriptions::kEnableNetworkServiceName,

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

@@ -2027,8 +2027,7 @@ void BrowserView::ViewHierarchyChanged(
 
 #if defined(USE_AURA)
   if (init) {
-    if (base::CommandLine::ForCurrentProcess()->HasSwitch(
-            switches::kEnableExperimentalFullscreenExitUI)) {
+    if (FullscreenControlHost::IsFullscreenExitUIEnabled()) {
       widget->GetNativeView()->AddPreTargetHandler(GetFullscreenControlHost());
     }
   } else if (fullscreen_control_host_) {

chrome/browser/ui/views/fullscreen_control/fullscreen_control_host.cc

@@ -5,9 +5,11 @@
 #include "chrome/browser/ui/views/fullscreen_control/fullscreen_control_host.h"
 
 #include "base/bind.h"
+#include "build/build_config.h"
 #include "chrome/browser/ui/views/exclusive_access_bubble_views.h"
 #include "chrome/browser/ui/views/frame/browser_view.h"
 #include "chrome/browser/ui/views/fullscreen_control/fullscreen_control_view.h"
+#include "chrome/common/chrome_features.h"
 #include "ui/events/event.h"
 #include "ui/events/event_constants.h"
 #include "ui/gfx/geometry/rect.h"
@@ -54,6 +56,17 @@ FullscreenControlHost::FullscreenControlHost(BrowserView* browser_view,
 
 FullscreenControlHost::~FullscreenControlHost() = default;
 
+// static
+bool FullscreenControlHost::IsFullscreenExitUIEnabled() {
+#if defined(OS_MACOSX)
+  // Exit UI is unnecessary, since Mac reveals the top chrome when the cursor
+  // moves to the top of the screen.
+  return false;
+#else
+  return base::FeatureList::IsEnabled(features::kFullscreenExitUI);
+#endif
+}
+
 void FullscreenControlHost::OnMouseEvent(ui::MouseEvent* event) {
   if (event->type() != ui::ET_MOUSE_MOVED ||
       fullscreen_control_popup_.IsAnimating() ||

chrome/browser/ui/views/fullscreen_control/fullscreen_control_host.h

@@ -30,6 +30,8 @@ class FullscreenControlHost : public ui::EventHandler {
                                  views::View* host_view);
   ~FullscreenControlHost() override;
 
+  static bool IsFullscreenExitUIEnabled();
+
   // ui::EventHandler:
   void OnMouseEvent(ui::MouseEvent* event) override;
   void OnTouchEvent(ui::TouchEvent* event) override;

chrome/browser/ui/views/fullscreen_control/fullscreen_control_view_interactive_uitest.cc

@@ -2,14 +2,14 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "base/command_line.h"
 #include "base/macros.h"
+#include "base/test/scoped_feature_list.h"
 #include "build/build_config.h"
 #include "chrome/browser/ui/exclusive_access/exclusive_access_bubble_type.h"
 #include "chrome/browser/ui/views/frame/browser_view.h"
 #include "chrome/browser/ui/views/fullscreen_control/fullscreen_control_host.h"
 #include "chrome/browser/ui/views/fullscreen_control/fullscreen_control_view.h"
-#include "chrome/common/chrome_switches.h"
+#include "chrome/common/chrome_features.h"
 #include "chrome/test/base/in_process_browser_test.h"
 #include "chrome/test/base/ui_test_utils.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -22,8 +22,9 @@ class FullscreenControlViewTest : public InProcessBrowserTest {
  public:
   FullscreenControlViewTest() = default;
 
-  void SetUpCommandLine(base::CommandLine* command_line) override {
-    command_line->AppendSwitch(switches::kEnableExperimentalFullscreenExitUI);
+  void SetUp() override {
+    scoped_feature_list_.InitAndEnableFeature(features::kFullscreenExitUI);
+    InProcessBrowserTest::SetUp();
   }
 
  protected:
@@ -42,6 +43,8 @@ class FullscreenControlViewTest : public InProcessBrowserTest {
   }
 
  private:
+  base::test::ScopedFeatureList scoped_feature_list_;
+
   DISALLOW_COPY_AND_ASSIGN(FullscreenControlViewTest);
 };
 

chrome/common/chrome_features.cc

@@ -276,6 +276,11 @@ const base::Feature kOpenVR{"OpenVR", base::FEATURE_DISABLED_BY_DEFAULT};
 
 #endif  // BUILDFLAG(ENABLE_VR)
 
+// Enables a floating action button-like full screen exit UI to allow exiting
+// fullscreen using mouse or touch.
+const base::Feature kFullscreenExitUI{"FullscreenExitUI",
+                                      base::FEATURE_DISABLED_BY_DEFAULT};
+
 #if defined(OS_WIN)
 // Enables using GDI to print text as simply text.
 const base::Feature kGdiTextPrinting {"GdiTextPrinting",

chrome/common/chrome_features.h

@@ -153,6 +153,8 @@ extern const base::Feature kOpenVR;
 
 #endif  // ENABLE_VR
 
+extern const base::Feature kFullscreenExitUI;
+
 #if defined(OS_MACOSX)
 extern const base::Feature kFullscreenToolbarReveal;
 #endif

chrome/common/chrome_switches.cc

@@ -295,11 +295,6 @@ const char kEnableDevToolsExperiments[]     = "enable-devtools-experiments";
 // Enables Domain Reliability Monitoring.
 const char kEnableDomainReliability[] = "enable-domain-reliability";
 
-// Enables an experimental full screen exit UI to allow exiting fullscreen from
-// mouse or touch.
-const char kEnableExperimentalFullscreenExitUI[] =
-    "enable-experimental-fullscreen-exit-ui";
-
 // Enables logging for extension activity.
 const char kEnableExtensionActivityLogging[] =
     "enable-extension-activity-logging";

chrome/common/chrome_switches.h

@@ -97,7 +97,6 @@ extern const char kEnableCloudPrintProxy[];
 extern const char kEnableDeviceDiscoveryNotifications[];
 extern const char kEnableDevToolsExperiments[];
 extern const char kEnableDomainReliability[];
-extern const char kEnableExperimentalFullscreenExitUI[];
 extern const char kEnableExtensionActivityLogging[];
 extern const char kEnableExtensionActivityLogTesting[];
 extern const char kEnableFastUnload[];

tools/metrics/histograms/enums.xml

@@ -26178,6 +26178,7 @@ from previous Chrome versions.
   <int value="-1633586675" label="TabModalJsDialog:enabled"/>
   <int value="-1631329950" label="ssl-version-max"/>
   <int value="-1630419335" label="enable-download-notification"/>
+  <int value="-1625881240" label="FullscreenExitUI:disabled"/>
   <int value="-1624854957" label="enable-es3-apis"/>
   <int value="-1620804800" label="NoScriptPreviews:disabled"/>
   <int value="-1620568042" label="FeaturePolicy:disabled"/>
@@ -27143,6 +27144,7 @@ from previous Chrome versions.
   <int value="679931272" label="DcheckIsFatal:enabled"/>
   <int value="680070635"
       label="enable-fullscreen-handwriting-virtual-keyboard:disabled"/>
+  <int value="681622885" label="FullscreenExitUI:enabled"/>
   <int value="682549212" label="ash-enable-cursor-motion-blur"/>
   <int value="684806628" label="TranslateLanguageByULP:disabled"/>
   <int value="685916283" label="enable-zip-archiver-on-file-manager"/>