Add UMA histograms for GPU driver bug workaround entries.

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 f8590d486b3abcb383de29989a2ea4fac121cc2d..a3e0b6178f034965c8442a8ff6dbcf0c57d9161f 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -22325,6 +22325,17 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="GPU.DriverBugTestResultsPerEntry">
+  <owner>jbauman@chromium.org</owner>
+  <owner>vmiura@chromium.org</owner>
+  <owner>kbr@chromium.org</owner>
+  <owner>zmo@chromium.org</owner>
+  <summary>
+    For every entry in the gpu driver bug list that is hit on a machine, this
+    records the id. Entry 0 is the total number of times that data is recorded.
+  </summary>
+</histogram>
+
 <histogram name="GPU.EGLDisplayType" enum="EGLDisplayType">
   <owner>jbauman@chromium.org</owner>
   <summary>The display type used to ask for an EGLDisplay.</summary>