Added a base::Callback interface to FilePathWatcher.

Added a base::Callback interface to FilePathWatcher.

BUG=130980
TEST=browser_tests:FilePathWatcher* are green

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=140285

[Mattias Nissler (ping if slow), 2012-06-04 12:26:39]

https://chromiumcodereview.appspot.com/10519003/diff/1/base/files/file_path_w...
File base/files/file_path_watcher.h (right):

https://chromiumcodereview.appspot.com/10519003/diff/1/base/files/file_path_w...
base/files/file_path_watcher.h:123: // called at most once, and from a
MessageLoop of TYPE_IO. The callback will
I'm wondering whether it'd be better if we just allowed any origin message loop,
s.t. you can easily watch files without having to worry about threads.

https://chromiumcodereview.appspot.com/10519003/diff/1/base/files/file_path_w...
File base/files/file_path_watcher_browsertest.cc (right):

https://chromiumcodereview.appspot.com/10519003/diff/1/base/files/file_path_w...
base/files/file_path_watcher_browsertest.cc:279: EXPECT_FALSE(called_back);
Is it safe to test the flag here that got written on a different thread here?
Also, spurious notifications may bite you here.

[Joao da Silva, 2012-06-04 12:45:42]

https://chromiumcodereview.appspot.com/10519003/diff/1/base/files/file_path_w...
File base/files/file_path_watcher.h (right):

https://chromiumcodereview.appspot.com/10519003/diff/1/base/files/file_path_w...
base/files/file_path_watcher.h:123: // called at most once, and from a
MessageLoop of TYPE_IO. The callback will
On 2012/06/04 12:26:39, Mattias Nissler wrote:
> I'm wondering whether it'd be better if we just allowed any origin message
loop,
> s.t. you can easily watch files without having to worry about threads.

The Watch() implementations do IO operations, so the current loop has to be
TYPE_IO; and usually there are IO operations too when callback is executed, so I
think this is a reasonable requirement.

https://chromiumcodereview.appspot.com/10519003/diff/1/base/files/file_path_w...
File base/files/file_path_watcher_browsertest.cc (right):

https://chromiumcodereview.appspot.com/10519003/diff/1/base/files/file_path_w...
base/files/file_path_watcher_browsertest.cc:279: EXPECT_FALSE(called_back);
On 2012/06/04 12:26:39, Mattias Nissler wrote:
> Is it safe to test the flag here that got written on a different thread here?
> Also, spurious notifications may bite you here.

The flag is written before the UI loop is unblocked, so it's safe to test the
flag below. But testing it here is indeed a bad idea; removed.

[Mattias Nissler (ping if slow), 2012-06-04 12:51:03]

LGTM

[commit-bot: I haz the power, 2012-06-04 13:02:25]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/joaodasilva@chromium.org/10519003/9001

[commit-bot: I haz the power, 2012-06-04 13:02:33]

Presubmit check for 10519003-9001 failed and returned exit status 1.

Running presubmit commit checks ...

** Presubmit Warnings **
New code should not use FilePathWatcher::Delegate. Use the callback interface
instead.
    base/files/file_path_watcher.cc:19
    base/files/file_path_watcher.cc:24
    base/files/file_path_watcher.h:117

Presubmit checks took 3.6s to calculate.