Instructions getting stack of errant view's construction

When a view fails an accessibility check, it can be very helpful to find
out what line of code constructed it. This provides information on how
to patch in code that does that.

We may want to build this in at some point:
See https://crrev.com/c/1025637 or https://crrev.com/c/963284.

Bug: 811293
Change-Id: I14046d7d40a5475e28691d371acdcb6538b66663
Reviewed-on: https://chromium-review.googlesource.com/1026055Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Commit-Queue: Aaron Leventhal <aleventhal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#553295}

chrome/test/views/accessibility_checker.cc

@@ -89,7 +89,10 @@ bool DoesViewHaveAccessibilityErrors(views::View* view,
       "The following view violates DoesViewHaveAccessibilityErrors() when its "
       "widget becomes " +
       std::string(view->GetWidget()->IsVisible() ? "visible:\n" : "hidden:\n") +
-      GetViewDebugString(view) + violations;
+      GetViewDebugString(view) + violations +
+      "\n\nNote: for a more useful error message that includes a stack of how "
+      "this view was constructed, use git cl patch 963284. Please leave a note "
+      "on that CL if you find it useful.";
   return true;
 }