Combine the WM_CHAR with WM_KEY* for key event flow.

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 ac3beae08058109ddd49442fbf903540423db7e7..56cd8e4bf412d5bd52e81dfc1cd19d356d505c72 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -9,6 +9,7 @@
 #include <set>
 #include <utility>
 
+#include "base/base_switches.h"
 #include "base/command_line.h"
 #include "base/memory/singleton.h"
 #include "base/metrics/sparse_histogram.h"
@@ -2129,6 +2130,12 @@ const Experiment kExperiments[] = {
       IDS_FLAGS_TRACE_EXPORT_EVENTS_TO_ETW_DESRIPTION,
       kOsWin,
       SINGLE_VALUE_TYPE(switches::kTraceExportEventsToETW)},
+    {"merge-key-char-events",
+     IDS_FLAGS_MERGE_KEY_CHAR_EVENTS_NAME,
+     IDS_FLAGS_MERGE_KEY_CHAR_EVENTS_DESCRIPTION,
+     kOsWin,
+     ENABLE_DISABLE_VALUE_TYPE(switches::kEnableMergeKeyCharEvents,
+                               switches::kDisableMergeKeyCharEvents)},
 #endif  // defined(OS_WIN)
     // NOTE: Adding new command-line switches requires adding corresponding
     // entries to enum "LoginCustomFlags" in histograms.xml. See note in