Check for the default search engine being null before using.

Check for the default search engine being null before using.

It is valid for the DSE to be null if DefaultSearchProviderEnabled
is false in the policy (see chrome://policy).

Check and appropriately handle null in all cases.

TEST=1.) Set "DefaultSearchProviderEnabled": false
     2.) Go to settings,
     3.) search engine marked as managed, disabled, and empty
TEST=1.) Set "DefaultSearchProviderEnabled": true,
         "DefaultSearchProviderSearchURL": "http://www.google.com/?q={searchTerms}",
         "DefaultSearchProviderKeyword": "google"
     2.) Go to settings
     3.) search engine marked as managed, disabled, show google

BUG=720504
Review-Url: https://codereview.chromium.org/2938403002
Cr-Original-Commit-Position: refs/heads/master@{#480234}
Review-Url: https://codereview.chromium.org/2950583002 .
Cr-Commit-Position: refs/branch-heads/3112@{#390}
Cr-Branched-From: b6460e24cf59f429d69de255538d0fc7a425ccf9-refs/heads/master@{#474897}
Committed: https://chromium.googlesource.com/chromium/src/+/3950ed79b024d9b541f17b89f523be392c91d5d4

[Ted C, 2017-06-19 20:06:43]

Description was changed from

==========
Check for the default search engine being null before using.

It is valid for the DSE to be null if DefaultSearchProviderEnabled
is false in the policy (see chrome://policy).

Check and appropriately handle null in all cases.

TEST=1.) Set "DefaultSearchProviderEnabled": false
     2.) Go to settings,
     3.) search engine marked as managed, disabled, and empty
TEST=1.) Set "DefaultSearchProviderEnabled": true,
         "DefaultSearchProviderSearchURL":
"http://www.google.com/?q={searchTerms}",
         "DefaultSearchProviderKeyword": "google"
     2.) Go to settings
     3.) search engine marked as managed, disabled, show google

BUG=720504

Review-Url: https://codereview.chromium.org/2938403002
Cr-Commit-Position: refs/heads/master@{#480234}
(cherry picked from commit 9c436a9669b2a3bc5cd10d8d75488715c8bf86aa)
==========

to

==========
Check for the default search engine being null before using.

It is valid for the DSE to be null if DefaultSearchProviderEnabled
is false in the policy (see chrome://policy).

Check and appropriately handle null in all cases.

TEST=1.) Set "DefaultSearchProviderEnabled": false
     2.) Go to settings,
     3.) search engine marked as managed, disabled, and empty
TEST=1.) Set "DefaultSearchProviderEnabled": true,
         "DefaultSearchProviderSearchURL":
"http://www.google.com/?q={searchTerms}",
         "DefaultSearchProviderKeyword": "google"
     2.) Go to settings
     3.) search engine marked as managed, disabled, show google

BUG=720504

Review-Url: https://codereview.chromium.org/2938403002
Cr-Original-Commit-Position: refs/heads/master@{#480234}
Review-Url: https://codereview.chromium.org/2950583002 .
Cr-Commit-Position: refs/branch-heads/3112@{#390}
Cr-Branched-From:
b6460e24cf59f429d69de255538d0fc7a425ccf9-refs/heads/master@{#474897}
Committed:
https://chromium.googlesource.com/chromium/src/+/3950ed79b024d9b541f17b89f523...
==========

[Ted C, 2017-06-19 20:06:44]

Committed patchset #1 (id:1) manually as
3950ed79b024d9b541f17b89f523be392c91d5d4.