Rename browser_action_test_util_views_mac.mm to browser_action_test_util_views_cocoa.mm

This allows browser_action_test_util_views_mac.mm to be used in the
future for shared code between Mac Views and Aura Views.

BUG=818397

Change-Id: I3c0937216233ffbbe1933ad3cbb423da1010feb2
Reviewed-on: https://chromium-review.googlesource.com/953245Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Commit-Queue: Robert Liao <robliao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#541632}

chrome/browser/ui/BUILD.gn

@@ -3896,7 +3896,7 @@ static_library("test_support") {
       }
     } else {
       sources += [
-        "cocoa/extensions/browser_action_test_util_views_mac.mm",
+        "cocoa/extensions/browser_action_test_util_views_cocoa.mm",
         "cocoa/find_bar/find_bar_host_unittest_util_cocoa.mm",
       ]
     }