Revert "Disable legacy touch event APIs on desktop"

This CL reverts commit a6a203c.
(crrev.com/c/729220)

We'll leave these feature detection API disabled in canary and
dev channel to gather some feedback. But don't let it in Beta
and Stable channel because it breaks embed map.

This revert will merge into into M68, but not landed in master branch

Bug: 804890
Change-Id: Ib017006081baf12b69fe137ba9aeae915b5274a3
Reviewed-on: https://chromium-review.googlesource.com/1081874
Reviewed-by: Ella Ge <eirage@chromium.org>
Cr-Commit-Position: refs/branch-heads/3440@{#85}
Cr-Branched-From: 010ddcf-refs/heads/master@{#561733}

chrome/browser/about_flags.cc

@@ -190,13 +190,13 @@ const unsigned kOsAura = kOsWin | kOsLinux | kOsCrOS;
 #endif  // USE_AURA
 
 const FeatureEntry::Choice kTouchEventFeatureDetectionChoices[] = {
-    {flags_ui::kGenericExperimentChoiceDisabled, "", ""},
+    {flags_ui::kGenericExperimentChoiceAutomatic, "", ""},
     {flags_ui::kGenericExperimentChoiceEnabled,
      switches::kTouchEventFeatureDetection,
      switches::kTouchEventFeatureDetectionEnabled},
-    {flags_ui::kGenericExperimentChoiceAutomatic,
+    {flags_ui::kGenericExperimentChoiceDisabled,
      switches::kTouchEventFeatureDetection,
-     switches::kTouchEventFeatureDetectionAuto}};
+     switches::kTouchEventFeatureDetectionDisabled}};
 
 #if defined(USE_AURA)
 const FeatureEntry::Choice kOverscrollHistoryNavigationChoices[] = {

chrome/browser/flag_descriptions.cc

@@ -1687,7 +1687,7 @@ const char kTouchEventsName[] = "Touch Events API";
 const char kTouchEventsDescription[] =
     "Force Touch Events API feature detection to always be enabled or "
     "disabled, or to be enabled when a touchscreen is detected on startup "
-    "(Automatic).";
+    "(Automatic, the default).";
 
 const char kTouchSelectionStrategyName[] = "Touch text selection strategy";
 const char kTouchSelectionStrategyDescription[] =

chrome/browser/prefs/chrome_pref_service_unittest.cc

@@ -4,7 +4,6 @@
 
 #include "base/command_line.h"
 #include "base/strings/utf_string_conversions.h"
-#include "build/build_config.h"
 #include "chrome/browser/prefs/chrome_command_line_pref_store.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/common/pref_names.h"
@@ -99,11 +98,4 @@ TEST_F(ChromePrefServiceWebKitPrefs, PrefsCopied) {
   EXPECT_EQ(base::ASCIIToUTF16(kDefaultFont),
             webkit_prefs.standard_font_family_map[prefs::kWebKitCommonScript]);
   EXPECT_TRUE(webkit_prefs.javascript_enabled);
-
-#if defined(OS_ANDROID)
-  // Touch event enabled only on Android.
-  EXPECT_TRUE(webkit_prefs.touch_event_feature_detection_enabled);
-#else
-  EXPECT_FALSE(webkit_prefs.touch_event_feature_detection_enabled);
-#endif
 }

content/browser/renderer_host/render_view_host_impl.cc

@@ -460,26 +460,18 @@ WebPreferences RenderViewHostImpl::ComputeWebkitPrefs() {
     NOTREACHED();
   }
 
-  // On Android, Touch event feature detection is enabled by default,
-  // Otherwise default is disabled.
-  std::string touch_enabled_default_switch =
-      switches::kTouchEventFeatureDetectionDisabled;
-#if defined(OS_ANDROID)
-  touch_enabled_default_switch = switches::kTouchEventFeatureDetectionEnabled;
-#endif  // defined(OS_ANDROID)
   const std::string touch_enabled_switch =
       command_line.HasSwitch(switches::kTouchEventFeatureDetection)
           ? command_line.GetSwitchValueASCII(
                 switches::kTouchEventFeatureDetection)
-          : touch_enabled_default_switch;
+          : switches::kTouchEventFeatureDetectionAuto;
   prefs.touch_event_feature_detection_enabled =
       (touch_enabled_switch == switches::kTouchEventFeatureDetectionAuto)
           ? (ui::GetTouchScreensAvailability() ==
              ui::TouchScreensAvailability::ENABLED)
           : (touch_enabled_switch.empty() ||
              touch_enabled_switch ==
                  switches::kTouchEventFeatureDetectionEnabled);
-
   std::tie(prefs.available_pointer_types, prefs.available_hover_types) =
       ui::GetAvailablePointerAndHoverTypes();
   prefs.primary_pointer_type =