Return string literals as const wchar_t*.

BUG=394842

Review URL: https://codereview.chromium.org/468303003

Cr-Commit-Position: refs/heads/master@{#289518}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@289518 0039d316-1c4b-4281-b951-d872f2087c98

chrome/common/terminate_on_heap_corruption_experiment_win.cc

@@ -22,7 +22,7 @@
 
 namespace {
 
-wchar_t* GetBeaconKeyPath() {
+const wchar_t* GetBeaconKeyPath() {
   chrome::VersionInfo::Channel channel = chrome::VersionInfo::CHANNEL_UNKNOWN;
 
   // We are called quite early, before the CommandLine is initialized. We don't