fix null check bugs found by µmix static analyzer

A Mozilla developer ran the µmix static analyzer on its codebase and incidentally found some issues regarding null checks in Skia. This fixes the issues that were found.

Downstream bug report: https://bugzilla.mozilla.org/show_bug.cgi?id=1278452

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2046563007

Committed: https://skia.googlesource.com/skia/+/2af4599b5c514933bf997d4837ddaaf24fc61cd7

[lsalzman1, 2016-06-08 01:39:28]

Description was changed from

==========
fix null check bugs found by µmix static analyzer

BUG=skia:
==========

to

==========
fix null check bugs found by µmix static analyzer

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2046563007
==========

[lsalzman1, 2016-06-08 01:42:34]

Description was changed from

==========
fix null check bugs found by µmix static analyzer

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2046563007
==========

to

==========
A Mozilla developer ran the µmix static analyzer on its codebase and
incidentally found some issues regarding null checks in Skia. This fixes the
issues that were found.

Downstream bug report: https://bugzilla.mozilla.org/show_bug.cgi?id=1278452

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2046563007
==========

[lsalzman1, 2016-06-08 01:42:35]

lsalzman@mozilla.com changed reviewers:
+ mtklein@google.com

[mtklein, 2016-06-08 01:56:30]

lgtm

FYI Cary and Ben: these look like cases where we've null-checked a pointer after
dereferencing it, which is always a bad idea.

[mtklein, 2016-06-08 01:56:34]

The CQ bit was checked by mtklein@google.com

[commit-bot: I haz the power, 2016-06-08 01:56:43]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/2046563007/1

[commit-bot: I haz the power, 2016-06-08 02:09:05]

Description was changed from

==========
A Mozilla developer ran the µmix static analyzer on its codebase and
incidentally found some issues regarding null checks in Skia. This fixes the
issues that were found.

Downstream bug report: https://bugzilla.mozilla.org/show_bug.cgi?id=1278452

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2046563007
==========

to

==========
A Mozilla developer ran the µmix static analyzer on its codebase and
incidentally found some issues regarding null checks in Skia. This fixes the
issues that were found.

Downstream bug report: https://bugzilla.mozilla.org/show_bug.cgi?id=1278452

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2046563007

Committed:
https://skia.googlesource.com/skia/+/2af4599b5c514933bf997d4837ddaaf24fc61cd7
==========

[commit-bot: I haz the power, 2016-06-08 02:09:06]

Committed patchset #1 (id:1) as
https://skia.googlesource.com/skia/+/2af4599b5c514933bf997d4837ddaaf24fc61cd7

[reed1, 2016-06-08 10:35:09]

reed@google.com changed reviewers:
+ bungeman@google.com, reed@google.com

[reed1, 2016-06-08 10:35:10]

Ben, some post-commit comments.

https://codereview.chromium.org/2046563007/diff/1/src/ports/SkFontMgr_win_dw.cpp
File src/ports/SkFontMgr_win_dw.cpp (right):

https://codereview.chromium.org/2046563007/diff/1/src/ports/SkFontMgr_win_dw....
src/ports/SkFontMgr_win_dw.cpp:112: *streamFontFileEnumerator = new
StreamFontFileEnumerator(factory, fontFileLoader);
This seems like a crazy test in the first place -- we NEVER assume that 'new'
will return nullptr. Ben?

https://codereview.chromium.org/2046563007/diff/1/src/utils/win/SkDWriteFontF...
File src/utils/win/SkDWriteFontFileStream.cpp (right):

https://codereview.chromium.org/2046563007/diff/1/src/utils/win/SkDWriteFontF...
src/utils/win/SkDWriteFontFileStream.cpp:142: if (nullptr ==
*streamFontFileStream) {
We NEVER assume 'new' will return nullptr. Can we remove this check?