The units for the CanvasExpansion should be pixels

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 eeea9193acb9d4e9a4283bcdc7b6759c2d6d35be..589a42d553b6c1858bcd2eea387689c576419ae1 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -3509,32 +3509,32 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
     determined. This is logged once per image header decode, which happens
     typically twice per image on the page.
   </summary>
 </histogram>
 
 <histogram name="Blink.DecodedImage.Orientation" enum="DecodedImageOrientation">
   <owner>rob.buis@samsung.org</owner>
   <summary>Image orientation inferred during decode.</summary>
 </histogram>
 
-<histogram name="Blink.DecodedImage.XCanvasExpansion" units="bytes">
+<histogram name="Blink.DecodedImage.XCanvasExpansion" units="pixels">
   <owner>ryansturm@chromium.org</owner>
   <owner>bengr@google.com</owner>
   <summary>
     How much the canvas width needed to be expanded as a result of the first
     frame's width and x-offset being larger than the initial canvas width. This
     is logged once per image header decode, which happens typically twice per
     image on the page.
   </summary>
 </histogram>
 
-<histogram name="Blink.DecodedImage.YCanvasExpansion" units="bytes">
+<histogram name="Blink.DecodedImage.YCanvasExpansion" units="pixels">
   <owner>ryansturm@chromium.org</owner>
   <owner>bengr@google.com</owner>
   <summary>
     How much the canvas height needed to be expanded as a result of the first
     frame's height and y-offset being larger than the initial canvas height.
     This is logged once per image header decode, which happens typically twice
     per image on the page.
   </summary>
 </histogram>