[backport] PR #8721 to 5.x

[elastic-jasper]

Backport PR #8721

Commit 1:
Stop Discover's Visualize button from loading incorrect URL

When App state is read from the url, it is accessed via
$location.search(). It turns out that the result of
$location.search() is a mutable object that allows you to modify the
results of $location.search() without actually modifying the URL. When
a user clicks a field in the Discover sidebar, it executes the scope
method vizLocation to get the href value for the "Visualize" button.
As an unintended side effect, vizLocation was modifying the object
returned from $location.search(). This change would ultimately be read
when the Visualize app loaded instead of the param in the actual URL
since there's no full page load from Discover -> Visualize.

To make things more complicated, I believe there was a race condition
partially masking this issue. Since vizLocation is used in an Angular
string template, the data binding causes it to execute on every digest
cycle. This is why the incorrect value continued to be written to
$location.search() even after visLocation ran for the correct field.
It also meant that the result of $location.search() was totally
dependent on which field vizLocation ran for most recently before the
user clicked Visualize.

Fixes #8718

• Original sha: d0d926b
• Authored by Matthew Bargar mbargar@gmail.com on 2016-10-17T21:07:11Z