Show alert failure for reloading unpacked extensions with bad manifest

chrome/browser/resources/extensions/extension_load_error.html

Index: chrome/browser/resources/extensions/extension_load_error.html
diff --git a/chrome/browser/resources/extensions/extension_load_error.html b/chrome/browser/resources/extensions/extension_load_error.html
index ce78dbcf745356367bf5a0f55da957ec488ea035..6feec95b2894b47d0a80dc85d614429a8cb7e21c 100644
--- a/chrome/browser/resources/extensions/extension_load_error.html
+++ b/chrome/browser/resources/extensions/extension_load_error.html
@@ -18,4 +18,8 @@ in the LICENSE file.
     <button id="extension-load-error-give-up-button"
             i18n-content="extensionLoadErrorGiveUp"></button>
   </div>
+  <div id="extension-load-error-additional" hidden>
+    <span i18n-content="extensionLoadAdditionalFailures"></span>
+    <ul></ul>
+  </div>

[Finnur, 2014/07/14 10:25:58]

I'm not sure I understand this new category. What additional failures are we
showing and why is necessary to add a separate category for them? Can we not use
one category for all failures?

The screenshot (http://i.imgur.com/02tzoUK.png) feels weird to me. Three
extensions failed to load but two have no error to show??

[gpdavis, 2014/07/14 18:58:19]

This list essentially functions as a stack, where the item on the top of the
stack is displayed.  When an unpacked installer fails, the UI pops up showing
the information about the manifest.  If any additional load failures are
triggered while this UI is still showing from the first error, then they are
pushed into this stack, and the original failure collapses into a list of failed
paths.  The new failure then has its manifest displayed.

This is the case in the screenshot.  Invalid three's manifest is showing because
it was the last failure to be triggered.  If you fix its manifest and reload it,
Invalid's failure gets popped off the stack into the UI, so its manifest is
displayed.  However, if the manifest is still broken, it will immediately
trigger another failure, pushing it back onto the stack so that it remains
visible.  Hitting "Give up" functions as you would expect; it drops the
currently displayed failure and pops the next one off the stack into the UI.

This is necessary because the UI only exists on the page in one place, and it
could get cluttered really quick if we were displaying the manifests of all the
extensions that failed to load.  If you refresh the extensions page, all the
unpacked extensions get reloaded, and they can all send errors to the UI
simultaneously.  This is why I chose to do it like a stack.

Does that make sense?  Can you think of a more reasonable way to approach it? 
I'd be happy to entertain any other possible implementations.

[Finnur, 2014/07/15 10:38:44]

Yes, that makes sense. I still think the labeling for the heading ("Additional
failures") is not helpful, but I'll add that comment elsewhere (in context).

 </div>