Clean up logic to determine if a navigation is from GWS.

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index 8c2e4430cd9743a675273cbb408994ecd291232d..045660f82feaa2ce183eb6e103efc312b17b1786 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -91386,18 +91386,21 @@ To add a new entry, add it with any value and run test to compute valid value.
     ordering="prefix">
   <suffix name="Clients.FromGWS"
       label="PageLoadMetrics that are a result of a navigation from a Google
+             web search">
+    <obsolete>
+      Deprecated in favor of Clients.FromGWS2.
+    </obsolete>
+  </suffix>
+  <suffix name="Clients.FromGWS2"
+      label="PageLoadMetrics that are a result of a navigation from a Google
              web search"/>
   <suffix name="Clients.DocWrite.Evaluator"
       label="PageLoadMetrics from a page that could have been evaluated by
              the DocumentWriteEvaluator"/>
   <affected-histogram
-      name="PageLoad.Timing2.DOMLoadingToDOMContentLoadedEventFired"/>
-  <affected-histogram name="PageLoad.Timing2.DOMLoadingToFirstContentfulPaint"/>
-  <affected-histogram
       name="PageLoad.Timing2.NavigationToDOMContentLoadedEventFired"/>
   <affected-histogram name="PageLoad.Timing2.NavigationToFirstContentfulPaint"/>
   <affected-histogram name="PageLoad.Timing2.NavigationToFirstImagePaint"/>
-  <affected-histogram name="PageLoad.Timing2.NavigationToFirstLayout"/>

[Alexei Svitkine (slow), 2016/04/19 19:57:55]

What's the reason for removing these?

If these were logged before, we would still want these entries so that old data
with suffixes can be decoded.

[Bryan McQuade, 2016/04/19 20:04:51]

We're deprecating these, but that's really separate from this change, so I
restored them here. We'll address the deprecation in a separate change.

   <affected-histogram name="PageLoad.Timing2.NavigationToFirstPaint"/>
   <affected-histogram name="PageLoad.Timing2.NavigationToFirstTextPaint"/>
   <affected-histogram name="PageLoad.Timing2.NavigationToLoadEventFired"/>