Add a switch for faking channels for Variations filtering.

chrome/browser/metrics/variations/variations_service.cc

Index: chrome/browser/metrics/variations/variations_service.cc
diff --git a/chrome/browser/metrics/variations/variations_service.cc b/chrome/browser/metrics/variations/variations_service.cc
index b4e12da5b1bb716dbe4b3ddb0f88b9d6b3ae6461..7fdf5f46c9e62519d1f03f2f18d8b352c43da387 100644
--- a/chrome/browser/metrics/variations/variations_service.cc
+++ b/chrome/browser/metrics/variations/variations_service.cc
@@ -277,12 +277,35 @@ bool VariationsService::StoreSeedData(const std::string& seed_data,
 }
 
 // static
+chrome::VersionInfo::Channel VariationsService::GetChannelForVariations() {

[Alexei Svitkine (slow), 2013/01/04 19:56:34]

Stick this in an anon namespace, since this isn't being used by tests. (The
other static functions are.)

Alternatively, add a test.

[SteveT, 2013/01/04 20:09:47]

Moved.

+  chrome::VersionInfo::Channel channel = chrome::VersionInfo::GetChannel();
+  if (channel != chrome::VersionInfo::CHANNEL_UNKNOWN)
+    return channel;
+  std::string forced_channel =
+      CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
+          switches::kFakeVariationsChannel);
+  if (!forced_channel.empty()) {

[Alexei Svitkine (slow), 2013/01/04 19:56:34]

Why this check?

[SteveT, 2013/01/04 20:09:47]

We won't need this anymore with the logging below. It was just to avoid hitting
the NOTREACHED when the switch is not provided.

+    if (forced_channel == "stable")
+      channel = chrome::VersionInfo::CHANNEL_STABLE;
+    else if (forced_channel == "beta")
+      channel = chrome::VersionInfo::CHANNEL_BETA;
+    else if (forced_channel == "dev")
+      channel = chrome::VersionInfo::CHANNEL_DEV;
+    else if (forced_channel == "canary")
+      channel = chrome::VersionInfo::CHANNEL_CANARY;
+    else
+      NOTREACHED();

[Alexei Svitkine (slow), 2013/01/04 19:56:34]

NOTREACHED() should be used for cases that shouldn't ever happen. In this case,
it would happen if someone specified some other string on the command-line, so
instead handle the case.

[SteveT, 2013/01/04 20:09:47]

Yeah you're right. I've DVLOGged instead, which I think is appropriate since
someone using this to test with Debug builds would want to see this output.

+  }
+  return channel;
+}
+
+// static
 bool VariationsService::ShouldAddStudy(
     const Study& study,
     const chrome::VersionInfo& version_info,
     const base::Time& reference_date) {
   if (study.has_filter()) {
-    if (!CheckStudyChannel(study.filter(), chrome::VersionInfo::GetChannel())) {
+    if (!CheckStudyChannel(study.filter(), GetChannelForVariations())) {
       DVLOG(1) << "Filtered out study " << study.name() << " due to channel.";
       return false;
     }