Fall back to static icon on privacy.resistFingerprinting. Fix #1357.

omega-target-chromium-extension/src/coffee/background.coffee

@@ -57,10 +57,15 @@ drawIcon = (resultColor, profileColor) ->
         drawOmega drawContext, profileColor
       drawContext.setTransform(1, 0, 0, 1, 0, 0)
       icon[size] = drawContext.getImageData(0, 0, size, size)
+      if icon[size].data[3] == 255
+        # Some browsers may replace the image data with a opaque white image to
+        # resist fingerprinting. In that case the icon cannot be drawn.
+        throw new Error('Icon drawing blocked by privacy.resistFingerprinting.')
   catch e
     if not drawError?
       drawError = e
       Log.error(e)
+      Log.error('Profile-colored icon disabled. Falling back to static icon.')
     icon = null
 
   return iconCache[cacheKey] = icon