Remove implicit conversions from scoped_refptr to T* in chrome/browser/sync_file_system/

Remove implicit conversions from scoped_refptr to T* in chrome/browser/sync_file_system/

This patch was generated by running the rewrite_scoped_refptr clang tool
on a Linux build.

BUG=110610
Committed: https://crrev.com/3b9b534f39c1b45858f5699afc763eff7d1bef0c
Cr-Commit-Position: refs/heads/master@{#292097}

[dcheng, 2014-08-26 00:24:09]

dcheng@chromium.org changed reviewers:
+ nhiroki@chromium.org

[dcheng, 2014-08-26 00:24:10]

Unfortunately, we can't make scoped_refptr testable until the conversion
operator has been removed. While it would be possible to disable the conversion
operator and make it testable in the same patch, the automated tool tries to
skip rewriting code where manual cleanups would be useful. This includes things
like:

// What if ReturnsScopedRefPtr() creates a new object internally?
if (ReturnsScopedRefPtr())

Foo* Bar() {
  const scoped_refptr<Foo>& f = ReturnsScopedRefPtr();
  return f;  // Does the return type need to be rewritten? Or is .get() safe?
}

Doing this in one patch would make catching some of these instances (in
particular, a boolean test on a temporary scoped_refptr) more difficult. As a
result, the work is being split into several steps:
Step 1: Rewrite all implicit conversions to be explicit (or rewrite the receiver
type to scoped_refptr<T>, if the tool believes the conversion to be unsafe).
Step 2: Once a platform compiles cleanly without the conversion operator, #ifdef
the conversion operator out.
Step 3: Make scoped_refptr testable on that platform.
Step 4: Remove unnecessary calls to .get().

[nhiroki, 2014-08-27 02:10:35]

lgtm

[dcheng, 2014-08-27 02:12:16]

The CQ bit was checked by dcheng@chromium.org

[commit-bot: I haz the power, 2014-08-27 02:12:43]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/dcheng@chromium.org/506793002/1

[commit-bot: I haz the power, 2014-08-27 04:03:24]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  linux_chromium_rel_swarming on tryserver.chromium.linux
(http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)

[commit-bot: I haz the power, 2014-08-27 04:38:40]

Committed patchset #1 (1) as 5e632bd3bdfbbfa9ae411f9588b7e5b7de5931a3

[commit-bot: I haz the power, 2014-09-10 02:49:43]

Patchset 1 (id:??) landed as
https://crrev.com/3b9b534f39c1b45858f5699afc763eff7d1bef0c
Cr-Commit-Position: refs/heads/master@{#292097}