Add MacRTL feature to flags

BUG=673362

Review-Url: https://codereview.chromium.org/2878563002
Cr-Commit-Position: refs/heads/master@{#471031}

chrome/browser/about_flags.cc

@@ -2904,6 +2904,12 @@ const FeatureEntry kFeatureEntries[] = {
      FEATURE_VALUE_TYPE(features::kOneGoogleBarOnLocalNtp)},
 #endif  // !defined(OS_ANDROID) && !defined(OS_IOS)
 
+#if defined(OS_MACOSX)
+    {"mac-rtl", flag_descriptions::kMacRTLName,
+     flag_descriptions::kMacRTLDescription, kOsMac,
+     FEATURE_VALUE_TYPE(features::kMacRTL)},
+#endif  // defined(OS_MACOSX)
+
     // NOTE: Adding new command-line switches requires adding corresponding
     // entries to enum "LoginCustomFlags" in histograms/enums.xml. See note in
     // enums.xml and don't forget to run AboutFlagsHistogramTest unit test.

chrome/browser/flag_descriptions.cc

@@ -3172,4 +3172,10 @@ const char kOneGoogleBarOnLocalNtpDescription[] =
 
 #endif  // !defined(OS_ANDROID) && !defined(OS_IOS)
 
+#if defined(OS_MACOSX)
+extern const char kMacRTLName[] = "Enable RTL";
+extern const char kMacRTLDescription[] =
+    "Mirrors the UI for RTL language users";
+#endif
+
 }  // namespace flag_descriptions

chrome/browser/flag_descriptions.h

@@ -3441,6 +3441,15 @@ extern const char kOneGoogleBarOnLocalNtpDescription[];
 
 #endif
 
+#if defined(OS_MACOSX)
+
+// Name and description of the flag that enables RTL in
+// Cocoa browser.
+extern const char kMacRTLName[];
+extern const char kMacRTLDescription[];
+
+#endif  // defined(OS_MACOSX)
+
 }  // namespace flag_descriptions
 
 #endif  // CHROME_BROWSER_FLAG_DESCRIPTIONS_H_

tools/metrics/histograms/enums.xml

@@ -21194,6 +21194,7 @@ from previous Chrome versions.
   <int value="-1943507605" label="enable-new-video-renderer"/>
   <int value="-1941852572" label="floating-virtual-keyboard"/>
   <int value="-1940806558" label="enable-syncfs-directory-operation"/>
+  <int value="-1940377152" label="MacRTL:enabled"/>
   <int value="-1940291343" label="SpeculativeResourcePrefetching:enabled"/>
   <int value="-1938263248" label="enable-extension-info-dialog"/>
   <int value="-1937077699" label="http-form-warning"/>
@@ -21540,6 +21541,7 @@ from previous Chrome versions.
   <int value="-697751423" label="disable-quickoffice-component-app"/>
   <int value="-684900739" label="disable-merge-key-char-events"/>
   <int value="-684223908" label="enable-android-wallpapers-app"/>
+  <int value="-680589442" label="MacRTL:disabled"/>
   <int value="-667517406" label="overscroll-history-navigation"/>
   <int value="-661978438" label="enable-data-reduction-proxy-lo-fi"/>
   <int value="-660160292" label="enable-apps-show-on-first-paint"/>