Add UMA histogram about what format of swapchain is created for overlays

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 7998373e7886759715f13674a5840879a77867ed..23cf22d5d60b393534f0d5d3ff8f58959a099fd8 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -21871,6 +21871,11 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <summary>Whether or not a frame displays an overlay.</summary>
 </histogram>
 
+<histogram name="GPU.DirectComposition.SwapchainFormat" enum="SwapchainFormat">
+  <owner>jbauman@chromium.org</owner>
+  <summary>What type of swapchain was actually created for an overlay.</summary>
+</histogram>
+
 <histogram name="GPU.DoLinkProgramTime" units="ms">
   <owner>jmadill@chromium.org</owner>
   <summary>
@@ -113015,6 +113020,11 @@ from previous Chrome versions.
   <int value="3" label="Attempted"/>
 </enum>
 
+<enum name="SwapchainFormat" type="int">
+  <int value="0" label="B8G8R8A8"/>
+  <int value="1" label="YUY2"/>
+</enum>
+
 <enum name="SwReporterRunningTimeRegistryError" type="int">
   <int value="0" label="No error"/>
   <int value="1" label="Registry key invalid"/>