Add UMA to measure how often pages don't receive any user input

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 84cf1f257732232a0f85d2b93c5bc3518f7e0f52..f24b30f4675ec5c4603823beb459c72cde844e06 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -41300,6 +41300,17 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram
+    name="PageLoad.Experimental.PaintTiming.FirstMeaningfulPaintSignalStatus"
+    enum="FirstMeaningfulPaintSignalStatus">
+  <owner>ksakamoto@chromium.org</owner>
+  <summary>
+    Whether the user had any interaction on the page (except mouse move) after
+    first paint, and whether the user left the page before network stable or
+    not.
+  </summary>
+</histogram>
+
 <histogram name="PageLoad.Experimental.PaintTiming.FirstMeaningfulPaintStatus"
     enum="FirstMeaningfulPaintStatus">
   <owner>ksakamoto@chromium.org</owner>
@@ -86824,6 +86835,13 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="20" label=".log"/>
 </enum>
 
+<enum name="FirstMeaningfulPaintSignalStatus" type="int">
+  <int value="0" label="No input, network active"/>
+  <int value="1" label="Had input, network active"/>
+  <int value="2" label="No input, network stable"/>
+  <int value="3" label="Had input, network stable"/>
+</enum>
+
 <enum name="FirstMeaningfulPaintStatus" type="int">
   <int value="0" label="Recorded successfully"/>
   <int value="1" label="The page was backgrounded"/>
@@ -107597,6 +107615,13 @@ value.
   <affected-histogram name="PLT.PT_StartToFinish_WithPreview"/>
 </histogram_suffixes>
 
+<histogram_suffixes name="HadUserInput" separator=".">
+  <suffix name="HadUserInput" label="Had user input"/>
+  <suffix name="NoUserInput" label="No user input"/>
+  <affected-histogram
+      name="PageLoad.Experimental.PaintTiming.NavigationToFirstMeaningfulPaint"/>
+</histogram_suffixes>
+
 <histogram_suffixes name="HandshakeConfirmed" separator=".">
   <suffix name="HandshakeConfirmed" label="the handshake was confirmed"/>
   <affected-histogram name="Net.QuicSession.ConnectionCloseErrorCodeClient"/>