[SPDY] Add histograms for flow control stalls

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 3f1dd0b7b6f46b2916dfe34ee53a34329d6ed047..cf39c1741971e1a90744ccef1df6c4d224979108 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -1929,6 +1929,22 @@ other types of suffix sets.
   <summary>Time from when the Connect() starts until it completes.</summary>
 </histogram>
 
+<histogram name="Net.SpdyFrameStreamAndSessionFlowControlState"
+    enum="SpdyFrameFlowControlState">
+  <summary>
+    The counts of the flow control state of each frame (with stream and session
+    flow control on).
+  </summary>
+</histogram>
+
+<histogram name="Net.SpdyFrameStreamFlowControlState"
+    enum="SpdyFrameFlowControlState">
+  <summary>
+    The counts of the flow control state of each frame (with stream flow control
+    on).
+  </summary>
+</histogram>
+
 <histogram name="Net.SpdyIPPoolDomainMatch" enum="SpdyIPPoolDomainMatch"
     units="count">
   <summary>
@@ -5567,6 +5583,13 @@ other types of suffix sets.
   <int value="2" label="wss"/>
 </enum>
 
+<enum name="SpdyFrameFlowControlState" type="int">
+  <int value="0" label="Send not stalled"/>
+  <int value="1" label="Send stalled by stream"/>
+  <int value="2" label="Send stalled by session"/>
+  <int value="3" label="Send stalled by stream and session"/>
+</enum>
+
 <enum name="SpdyIPPoolDomainMatch" type="int">
   <int value="0" label="mismatch"/>
   <int value="1" label="match"/>