Bug 1400357 - Whitelist maximize.svg in browser_startup_images. r=florian, a=test-only

There have been changes to our Windows infrastructure that cause the
window to be maximized when running tests so the maximize.svg/restore.svg
combination will show restore instead of maximize, though maximize is
still loaded. I think it could be prevented by trying to set the sizemode
attribute a little earlier or not defaulting to maximize in the stylesheet,
but I don't think that's a necessary optimization at this point. We can
just whitelist it.

I also set the intermittentShown flag in case the Windows machines go back
to non-maximized windows.

MozReview-Commit-ID: Gwi0jRBBtGg

--HG--
extra : source : 43983cf4138e13ba21b1a4cdcf21ab56336cedff

browser/base/content/test/performance/browser_startup_images.js

@@ -34,6 +34,8 @@ const whitelist = [
     file: "chrome://browser/skin/places/toolbarDropMarker.png",
     platforms: ["linux", "win", "macosx"],
   },
+
+  // Bug 1363040
   {
     file: "chrome://browser/skin/tracking-protection-16.svg#enabled",
     platforms: ["linux", "win", "macosx"],
@@ -71,6 +73,16 @@ const whitelist = [
     file: "chrome://global/skin/icons/resizer.png",
     platforms: ["win"],
   },
+
+  {
+    file: "chrome://browser/skin/window-controls/maximize.svg",
+    platforms: ["win"],
+    // This is to prevent perma-fails in case Windows machines
+    // go back to running tests in non-maximized windows.
+    intermittentShown: ["win"],
+    // This file is not loaded on Windows 7/8.
+    intermittentNotLoaded: ["win"],
+  },
 ];
 
 add_task(async function() {

browser/base/content/test/performance/hidpi/browser.ini

@@ -3,4 +3,4 @@ prefs =
   layout.css.devPixelsPerPx='2'
 
 [../browser_startup_images.js]
-skip-if = !debug || (os == 'win' && (os_version == '6.1' || os_version == '10.0'))  # hidpi results in the toolbar overflowing on Win 7; fails on Win 10 (bug 1400357)
+skip-if = !debug || (os == 'win' && (os_version == '6.1'))  # hidpi results in the toolbar overflowing on Win 7