Don't initialize decryptor on CDM creation failure

Don't initialize decryptor on CDM creation failure

PpapiDecryptor::Create() must not proceed with decryptor initialization
if the CDM wrapper could not be created.
PpapiDecryptor::PpapiDecryptor() asserts the CDM wrapper is valid and
InitializeCdm() uses it unconditionally.

BUG=488363
TEST=EME tests pass

Committed: https://crrev.com/4590f922ab1449f86e8d4ad43047de47d7790610
Cr-Commit-Position: refs/heads/master@{#330150}

[wdzierzanowski, 2015-05-15 10:57:35]

wdzierzanowski@opera.com changed reviewers:
+ jrummell@chromium.org

[wdzierzanowski, 2015-05-15 10:57:35]

jrummell, PTAL. I think a return statement was needlessly removed in
https://codereview.chromium.org/1102363005/diff/80001/content/renderer/media/....

[jrummell, 2015-05-15 17:00:10]

lgtm. Thanks for fixing this.

[ddorwin, 2015-05-15 17:59:37]

The CQ bit was checked by ddorwin@chromium.org

[commit-bot: I haz the power, 2015-05-15 18:01:12]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1128693004/1

[commit-bot: I haz the power, 2015-05-15 18:57:33]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-05-15 18:58:22]

Patchset 1 (id:??) landed as
https://crrev.com/4590f922ab1449f86e8d4ad43047de47d7790610
Cr-Commit-Position: refs/heads/master@{#330150}