Add about://flags entry for tab scrolling.

Bug: 951078
Change-Id: Id66be9ff30e334f53338fa9848fa73db3ea318ff
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1560373
Commit-Queue: Charlene Yan <cyan@chromium.org>
Reviewed-by: Taylor Bergquist <tbergquist@chromium.org>
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Cr-Commit-Position: refs/heads/master@{#650509}

chrome/browser/about_flags.cc

@@ -2798,6 +2798,10 @@ const FeatureEntry kFeatureEntries[] = {
      flag_descriptions::kTabGroupsDescription, kOsDesktop,
      FEATURE_VALUE_TYPE(features::kTabGroups)},
 
+    {"scrollable-tabstrip", flag_descriptions::kScrollableTabStripName,
+     flag_descriptions::kScrollableTabStripDescription, kOsDesktop,
+     FEATURE_VALUE_TYPE(features::kScrollableTabStrip)},
+
 #if defined(OS_ANDROID)
     {"dont-prefetch-libraries", flag_descriptions::kDontPrefetchLibrariesName,
      flag_descriptions::kDontPrefetchLibrariesDescription, kOsAndroid,

chrome/browser/flag-metadata.json

@@ -2931,6 +2931,11 @@
     "owners": [ "dfried", "corising", "//chrome/browser/ui/views/tabs/OWNERS" ],
     "expiry_milestone": 82
   },
+  {
+    "name": "scrollable-tabstrip",
+    "owners": ["chrome-desktop-ui-seattle@google.com", "tbergquist"],
+    "expiry_milestone": 82
+  },
   {
     "name": "tint-gl-composited-content",
     "owners": [ "chromeos-gfx@google.com" ],

chrome/browser/flag_descriptions.cc

@@ -1724,6 +1724,11 @@ const char kSaveasMenuLabelExperimentDescription[] =
     "Enables an experiment to switch menu labels that use 'Save as...' to "
     "'Download'.";
 
+const char kScrollableTabStripName[] = "Scrollable TabStrip";
+const char kScrollableTabStripDescription[] =
+    "Allows users to access tabs by scrolling when they no longer fit in the "
+    "tabstrip.";
+
 const char kSendTabToSelfName[] = "Send tab to self";
 const char kSendTabToSelfDescription[] =
     "Allows users to receive tabs from other synced devices, in order to "

chrome/browser/flag_descriptions.h

@@ -1030,6 +1030,9 @@ extern const char kSamplingHeapProfilerDescription[];
 extern const char kSaveasMenuLabelExperimentName[];
 extern const char kSaveasMenuLabelExperimentDescription[];
 
+extern const char kScrollableTabStripName[];
+extern const char kScrollableTabStripDescription[];
+
 extern const char kSendTabToSelfName[];
 extern const char kSendTabToSelfDescription[];
 

chrome/browser/ui/ui_features.cc

@@ -10,6 +10,10 @@ namespace features {
 const base::Feature kExtensionsToolbarMenu{"ExtensionsToolbarMenu",
                                            base::FEATURE_DISABLED_BY_DEFAULT};
 
+// Enables tabs to scroll in the tabstrip. https://crbug.com/951078
+const base::Feature kScrollableTabStrip{"ScrollableTabStrip",
+                                        base::FEATURE_DISABLED_BY_DEFAULT};
+
 // Enables grouping tabs together in the tab strip. https://crbug.com/905491
 const base::Feature kTabGroups{"TabGroups", base::FEATURE_DISABLED_BY_DEFAULT};
 

chrome/browser/ui/ui_features.h

@@ -18,6 +18,8 @@ namespace features {
 
 extern const base::Feature kExtensionsToolbarMenu;
 
+extern const base::Feature kScrollableTabStrip;
+
 extern const base::Feature kTabGroups;
 
 extern const base::Feature kTabHoverCards;

tools/metrics/histograms/enums.xml

@@ -32038,6 +32038,7 @@ Called by update_gpu_driver_bug_workaround_entries.py.-->
   <int value="-2143328006"
       label="enable-fill-on-account-select-no-highlighting"/>
   <int value="-2143113994" label="enable-ephemeral-apps-in-webstore"/>
+  <int value="-2142665444" label="ScrollableTabStrip:disabled"/>
   <int value="-2141661938" label="AnimatedAppMenuIcon:enabled"/>
   <int value="-2141247271" label="AndroidOmniboxPreviewsBadge:enabled"/>
   <int value="-2134333982" label="ShowArcFilesApp:enabled"/>
@@ -34659,6 +34660,7 @@ from previous Chrome versions.
   <int value="1938279796" label="PromosOnLocalNtp:disabled"/>
   <int value="1939413645" label="enable-invalid-cert-collection"/>
   <int value="1940625534" label="NewOverviewUi:disabled"/>
+  <int value="1941845443" label="ScrollableTabStrip:enabled"/>
   <int value="1942911276" label="enable-grouped-history"/>
   <int value="1944156526" label="sync-url"/>
   <int value="1947350992" label="drop-sync-credential:disabled"/>