Add a flag to enable/disable ordinal motion in Exo

In crrev.com/c/2277694, mouse movement events on CrOS will have ordinal
motion. We add a flag that will be used to control whether Exo reads
those, or just continues to use accelerated motion.

We want a flag in the short term because the hardware units we get on
CrOS are too small, and we require some investigation in how to scale
them appropriately.

Bug: b/161755250
Change-Id: I3ac45b020d033a8fe180789bd979e7a50a68e0ef
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2370683
Commit-Queue: Nic Hollingum <hollingum@google.com>
Reviewed-by: Jun Mukai <mukai@chromium.org>
Cr-Commit-Position: refs/heads/master@{#804835}

chrome/browser/about_flags.cc

@@ -5816,6 +5816,12 @@ const FeatureEntry kFeatureEntries[] = {
      FEATURE_VALUE_TYPE(features::kMacCoreLocationImplementation)},
 #endif
 
+#if defined(OS_CHROMEOS)
+    {"exo-ordinal-motion", flag_descriptions::kExoOrdinalMotionName,
+     flag_descriptions::kExoOrdinalMotionDescription, kOsCrOS,
+     FEATURE_VALUE_TYPE(chromeos::features::kExoOrdinalMotion)},
+#endif  // defined(OS_CHROMEOS)
+
 #if defined(OS_CHROMEOS)
     {"exo-pointer-lock", flag_descriptions::kExoPointerLockName,
      flag_descriptions::kExoPointerLockDescription, kOsCrOS,

chrome/browser/flag-metadata.json

@@ -2418,6 +2418,11 @@
     "owners": [ "cthomp" ],
     "expiry_milestone": 83
   },
+  {
+    "name": "exo-ordinal-motion",
+    "owners": [ "hollingum@google.com" ],
+    "expiry_milestone": 90
+  },
   {
     "name": "exo-pointer-lock",
     "owners": [ "hollingum@google.com" ],

chrome/browser/flag_descriptions.cc

@@ -4006,6 +4006,11 @@ const char kEnterpriseReportingInChromeOSDescription[] =
     "Enable the enterprise cloud reporting in Chrome OS. This feature requires "
     "user level cloud management.";
 
+const char kExoOrdinalMotionName[] =
+    "Raw (unaccelerated) motion for Linux applications";
+const char kExoOrdinalMotionDescription[] =
+    "Send unaccelerated values as raw motion events to linux applications.";
+
 const char kExoPointerLockName[] = "Pointer lock for Linux applications";
 const char kExoPointerLockDescription[] =
     "Allow Linux applications to request a pointer lock, i.e. exclusive use of "

chrome/browser/flag_descriptions.h

@@ -2321,6 +2321,9 @@ extern const char kEnableSuggestedFilesDescription[];
 extern const char kEnterpriseReportingInChromeOSName[];
 extern const char kEnterpriseReportingInChromeOSDescription[];
 
+extern const char kExoOrdinalMotionName[];
+extern const char kExoOrdinalMotionDescription[];
+
 extern const char kExoPointerLockName[];
 extern const char kExoPointerLockDescription[];
 

chromeos/constants/chromeos_features.cc

@@ -189,6 +189,10 @@ const base::Feature kEmojiSuggestAddition{"EmojiSuggestAddition",
 const base::Feature kEolWarningNotifications{"EolWarningNotifications",
                                              base::FEATURE_ENABLED_BY_DEFAULT};
 
+// Enable or disable use of ordinal (unaccelerated) motion by Exo clients.
+const base::Feature kExoOrdinalMotion{"ExoOrdinalMotion",
+                                      base::FEATURE_DISABLED_BY_DEFAULT};
+
 // Enable or disable pointer lock for Crostini windows.
 const base::Feature kExoPointerLock{"ExoPointerLock",
                                     base::FEATURE_DISABLED_BY_DEFAULT};

chromeos/constants/chromeos_features.h

@@ -88,6 +88,8 @@ extern const base::Feature kEmojiSuggestAddition;
 COMPONENT_EXPORT(CHROMEOS_CONSTANTS)
 extern const base::Feature kEolWarningNotifications;
 COMPONENT_EXPORT(CHROMEOS_CONSTANTS)
+extern const base::Feature kExoOrdinalMotion;
+COMPONENT_EXPORT(CHROMEOS_CONSTANTS)
 extern const base::Feature kExoPointerLock;
 COMPONENT_EXPORT(CHROMEOS_CONSTANTS) extern const base::Feature kFilesNG;
 COMPONENT_EXPORT(CHROMEOS_CONSTANTS) extern const base::Feature kFilesSWA;

tools/metrics/histograms/enums.xml

@@ -42197,6 +42197,7 @@ from previous Chrome versions.
   <int value="-299841473" label="top-document-isolation:enabled"/>
   <int value="-297716805"
       label="CrossOriginMediaPlaybackRequiresUserGesture:disabled"/>
+  <int value="-296762162" label="ExoOrdinalMotion:enabled"/>
   <int value="-296179618" label="CookiesWithoutSameSiteMustBeSecure:enabled"/>
   <int value="-295237704" label="EnableRemovingAllThirdPartyCookies:enabled"/>
   <int value="-290672626" label="enable-asm-wasm"/>
@@ -43179,6 +43180,7 @@ from previous Chrome versions.
   <int value="736911267" label="ExperimentalCrostiniUI:disabled"/>
   <int value="737421745" label="enable-accessibility-object-model"/>
   <int value="738868972" label="GdiTextPrinting:disabled"/>
+  <int value="738962107" label="ExoOrdinalMotion:disabled"/>
   <int value="739938466"
       label="WebPaymentsPerMethodCanMakePaymentQuota:disabled"/>
   <int value="740056959" label="ImeServiceConnectable:enabled"/>