Expose Touchable Chrome to all platforms

This CL exposes the Touchable Chrome flag to all platforms
and updates the flag description.

BUG=801582

Change-Id: Ic261824c1e32c1a1c17f522d7416a75c99a53bf4
Reviewed-on: https://chromium-review.googlesource.com/944101
Commit-Queue: Ahmed Fakhry <afakhry@chromium.org>
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Reviewed-by: Trent Apted <tapted@chromium.org>
Cr-Commit-Position: refs/heads/master@{#540388}

chrome/browser/about_flags.cc

@@ -464,12 +464,8 @@ const FeatureEntry::Choice kTopChromeMaterialDesignChoices[] = {
      switches::kTopChromeMDMaterialHybrid},
     {flag_descriptions::kTopChromeMdMaterialAuto, switches::kTopChromeMD,
      switches::kTopChromeMDMaterialAuto},
-#if defined(OS_LINUX)
-    // Exposed on Linux and ChromeOS: Windows/Mac support is too rough.
     {flag_descriptions::kTopChromeMdMaterialTouchOptimized,
-     switches::kTopChromeMD, switches::kTopChromeMDMaterialTouchOptimized},
-#endif
-};
+     switches::kTopChromeMD, switches::kTopChromeMDMaterialTouchOptimized}};
 
 #if defined(OS_CHROMEOS)
 const FeatureEntry::Choice kAshShelfColorChoices[] = {

chrome/browser/flag_descriptions.cc

@@ -1523,11 +1523,13 @@ const char kTintGlCompositedContentDescription[] =
 
 const char kTopChromeMd[] = "UI Layout for the browser's top chrome";
 const char kTopChromeMdDescription[] =
-    R"*(Toggles between normal and touch/hybrid layouts.)*";
+    "Toggles between 1) Normal - for clamshell devices, 2) Hybrid (previously "
+    "touch) - middle point for devices with a touch screen, and 3) Touchable "
+    "- new unified interface for touch and convertibles (Chrome OS).";
 const char kTopChromeMdMaterial[] = "Normal";
 const char kTopChromeMdMaterialAuto[] = "Auto";
 const char kTopChromeMdMaterialHybrid[] = "Hybrid";
-const char kTopChromeMdMaterialTouchOptimized[] = "Touch";
+const char kTopChromeMdMaterialTouchOptimized[] = "Touchable";
 
 const char kThreadedScrollingName[] = "Threaded scrolling";
 const char kThreadedScrollingDescription[] =