Let IsComposited expire, push back offscreen canvas metrics

Blink.OffscreenCanvas.NewOffscreenCanvas and OffscreenCanvas.Transferred
are still giving us good data, push back their expiry to next year with
other canvas metrics.

I did the same for IsComposited last week, but looking into it it looks
like we've been getting bad data from it for at least a year. It is
redundant with isAccelerated anyway, so change it back to the old date
to let it expire.

Bug: 1160792, 1160789
Change-Id: I7fcd0f1d9a2c92059c8b2ddeec7280c061e019c3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2625288Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Reviewed-by: Aaron Krajeski <aaronhk@chromium.org>
Commit-Queue: Aaron Krajeski <aaronhk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#842737}

tools/metrics/histograms/histograms_xml/blink/histograms.xml

@@ -172,12 +172,16 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 </histogram>
 
 <histogram name="Blink.Canvas.IsComposited" enum="Boolean"
-    expires_after="2022-04-04">
+    expires_after="2021-01-31">
   <owner>aaronhk@chromium.org</owner>
   <owner>fserb@chromium.org</owner>
   <summary>
     Records if the canvas context is composited or not. Recorded in
     HTMLCanvasElement::GetCanvasRenderingContext.
+
+    Note: This has been recording bad data since at least 2020-01-01. It was
+    emitted in the wrong place and always recording false. Since it records the
+    same information as IsAccelerated, I am just going to let it expire.
   </summary>
 </histogram>
 
@@ -1645,7 +1649,7 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 </histogram>
 
 <histogram name="Blink.OffscreenCanvas.NewOffscreenCanvas" enum="Boolean"
-    expires_after="2021-01-31">
+    expires_after="2022-04-04">
   <owner>aaronhk@chromium.org</owner>
   <owner>fserb@chromium.org</owner>
   <summary>
@@ -1671,7 +1675,7 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 </histogram>
 
 <histogram name="Blink.OffscreenCanvas.Transferred" enum="Boolean"
-    expires_after="2021-01-31">
+    expires_after="2022-04-04">
   <owner>aaronhk@chromium.org</owner>
   <owner>fserb@chromium.org</owner>
   <summary>