Add enable flag for pointer events in about://flags

chrome/browser/about_flags.cc

Index: chrome/browser/about_flags.cc
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index 161a82308a840424029126de8054d3cc0305322a..08611c3f500f529bfc9a4db581d2eb0501907406 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -2114,6 +2114,13 @@ const FeatureEntry kFeatureEntries[] = {
          switches::kMarketUrlForTesting,
          "https://play.google.com/store/apps/details?id=com.android.chrome")},
 #endif  // OS_ANDROID
+    {"enable-pointerevents",  // FLAGS:RECORD_UMA
+      IDS_FLAGS_EXPERIMENTAL_POINTER_EVENT_NAME,
+      IDS_FLAGS_EXPERIMENTAL_POINTER_EVENT_DESCRIPTION,
+      kOsAll,
+      SINGLE_VALUE_TYPE_AND_VALUE(
+          switches::kEnableBlinkFeatures,

[Rick Byers, 2016/01/07 19:49:02]

I got some flack for using this cheapo approach to enabling specific blink
features by flags - see crbug.com/536913.  The problem is that
--enable-blink-features causes a scary "potential unsafe flag" warning and users
are confused about what triggered it.

An infobar itself isn't bad - we don't want users to forget they have an
incomplete feature enabled.  But if there's going to be an infobar, the text
should direct them to the actual flag they enabled.

So I think either we need to:
 1) just do the plumbing to add another switch (content_switches.cc) which
ultimately has the same effect as --enable-blink-features=PointerEvent, or
 2) Add some mechanism for customizing the text displayed when a flag is
enabled.

[mustaq, 2016/01/07 20:13:06]

I think a separate entry in content_switches is better. Customizing the infobar
text only for this one seems a bit overkill to me:
https://code.google.com/p/chromium/codesearch#chromium/src/chrome/browser/ui/...

[Navid Zolghadr, 2016/01/08 16:50:09]

Done.

+          "PointerEvent")},
     // NOTE: Adding new command-line switches requires adding corresponding
     // entries to enum "LoginCustomFlags" in histograms.xml. See note in
     // histograms.xml and don't forget to run AboutFlagsHistogramTest unit test.