Correctly whitelist the PDF plugin in the PDF extension.

Correctly whitelist the PDF plugin in the PDF extension.

For plugins listed in
chrome/browser/resources/plugin_metadata/plugins_*.json, the resource
identifier for that plugin becomes the key used in those JSON files.
Previously, the PDF plugin filename was used as the resource identifier
to whitelist the PDF plugin within the PDF extension. This caused the
whitelisting to be ineffective for official builds and also other builds
after r316957 added an entry for the Chromium PDF Viewer plugin. This CL
fixes this by using the keys from the plugin metadata files as the
resource identifiers for whitelisting the PDF plugin.

BUG=459998
Committed: https://crrev.com/2c8ef923fc3a440aa99b09372fde8f3d0893f551
Cr-Commit-Position: refs/heads/master@{#317556}

[Sam McNally, 2015-02-23 00:07:39]

sammc@chromium.org changed reviewers:
+ bauerb@chromium.org, raymes@chromium.org

[Sam McNally, 2015-02-23 00:07:40]

+bauerb for
chrome/browser/content_settings/content_settings_internal_extension_provider.cc

+raymes for chrome/browser/pdf

[raymes, 2015-02-23 00:11:18]

lgtm

[Bernhard Bauer, 2015-02-23 10:01:37]

lgtm

[Sam McNally, 2015-02-23 10:02:47]

The CQ bit was checked by sammc@chromium.org

[commit-bot: I haz the power, 2015-02-23 10:03:19]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/946293002/1

[commit-bot: I haz the power, 2015-02-23 10:13:50]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-23 10:14:47]

Patchset 1 (id:??) landed as
https://crrev.com/2c8ef923fc3a440aa99b09372fde8f3d0893f551
Cr-Commit-Position: refs/heads/master@{#317556}