Add APCA to the DevToolsColorPickerFixedColor enum

Bug: 1121900
Change-Id: I579156dd5b9411324fb88b76bbd12bfb17397d67
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2537633Reviewed-by: Mathias Bynens <mathias@chromium.org>
Commit-Queue: Alex Rudenko <alexrudenko@chromium.org>
Cr-Commit-Position: refs/heads/master@{#827728}

tools/metrics/histograms/enums.xml

@@ -16640,6 +16640,7 @@ metrics consent we also won't be able to send UMA metrics. -->
 <enum name="DevToolsColorPickerFixedColor">
   <int value="0" label="AA"/>
   <int value="1" label="AAA"/>
+  <int value="2" label="APCA"/>
 </enum>
 
 <enum name="DevToolsComputedStyleGrouping">