Reland of Android: Trust large random numbers for temp files

Reland of Android: Trust large random numbers for temp files (patchset #1 id:1 of https://codereview.chromium.org/1412433003/ )

Reason for revert:
Relanding with fix for ReadFile(as_root=True)

Original issue's description:
> Revert of Android: Trust large random numbers for temp files (patchset #1 id:1 of https://codereview.chromium.org/1402353002/ )
>
> Reason for revert:
> Likely cause of Android GN breakage in stack_tool_for_tombstones:
> https://build.chromium.org/p/chromium.linux/builders/Android%20GN/builds/31358
>
> Traceback (most recent call last):
>   File "/b/build/slave/Android_GN/build/src/build/android/tombstones.py", line 257, in <module>
>     sys.exit(main())
>   File "/b/build/slave/Android_GN/build/src/build/android/tombstones.py", line 251, in main
>     tombstones += _GetTombstonesForDevice(device, options)
>   File "/b/build/slave/Android_GN/build/src/build/android/tombstones.py", line 197, in _GetTombstonesForDevice
>     'data': _GetTombstoneData(device, tombstone_file)}]
>   File "/b/build/slave/Android_GN/build/src/build/android/tombstones.py", line 79, in _GetTombstoneData
>     '/data/tombstones/' + tombstone_file, as_root=True).splitlines()
>   File "/b/build/slave/Android_GN/build/src/build/android/devil/android/decorators.py", line 53, in timeout_retry_wrapper
>     return timeout_retry.Run(impl, timeout, retries, desc=desc)
>   File "/b/build/slave/Android_GN/build/src/build/android/devil/utils/timeout_retry.py", line 161, in Run
>     error_log_func=error_log_func)
>   File "/b/build/slave/Android_GN/build/src/build/android/devil/utils/reraiser_thread.py", line 186, in JoinAll
>     self._JoinAll(watcher, timeout)
>   File "/b/build/slave/Android_GN/build/src/build/android/devil/utils/reraiser_thread.py", line 158, in _JoinAll
>     thread.ReraiseIfException()
>   File "/b/build/slave/Android_GN/build/src/build/android/devil/utils/reraiser_thread.py", line 81, in run
>     self._ret = self._func(*self._args, **self._kwargs)
>   File "/b/build/slave/Android_GN/build/src/build/android/devil/utils/timeout_retry.py", line 154, in <lambda>
>     child_thread = reraiser_thread.ReraiserThread(lambda: func(*args, **kwargs),
>   File "/b/build/slave/Android_GN/build/src/build/android/devil/android/decorators.py", line 44, in impl
>     return f(*args, **kwargs)
>   File "/b/build/slave/Android_GN/build/src/build/android/devil/android/device_utils.py", line 1441, in ReadFile
>     return self._ReadFileWithPull(device_temp.name)
>   File "/b/build/slave/Android_GN/build/src/build/android/devil/android/device_utils.py", line 1384, in _ReadFileWithPull
>     self.adb.Pull(device_path, host_temp_path)
>   File "/b/build/slave/Android_GN/build/src/build/android/devil/android/sdk/adb_wrapper.py", line 247, in Pull
>     cmd, 'File not found on host: %s' % local, device_serial=str(self))
> devil.android.device_errors.AdbCommandFailedError: (device: 0528be3e0a286d60) adb pull /data/local/tmp/temp_file-ff7f09e4cdfa0 /tmp/tmpYJtAXL/tmp_ReadFileWithPull: failed and output:
> - File not found on host: /tmp/tmpYJtAXL/tmp_ReadFileWithPull
>
> Original issue's description:
> > Android: Trust large random numbers for temp files
> >
> > Saves a good amount of time (150ms per) and log pollution to not execute an adb
> > command for each temp file.
> >
> > BUG=540857
> >
> > Committed: https://crrev.com/a5a882f8e9325c782db666c27831cc82f119ced7
> > Cr-Commit-Position: refs/heads/master@{#354332}
>
> TBR=jbudorick@chromium.org,agrieve@chromium.org
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=540857
>
> Committed: https://crrev.com/011b0059489c76c8ef45456ef8131217398c4fad
> Cr-Commit-Position: refs/heads/master@{#354367}

BUG=540857
Committed: https://crrev.com/fc5b96fe6e0b196889a3aba6ba016b471e9cf510
Cr-Commit-Position: refs/heads/master@{#354516}

[agrieve, 2015-10-16 00:49:23]

Created Reland of Android: Trust large random numbers for temp files

[agrieve, 2015-10-16 00:56:03]

The CQ bit was checked by agrieve@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-10-16 00:56:58]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1410553004/70001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1410553004/70001

[agrieve, 2015-10-16 01:02:26]

The CQ bit was unchecked by agrieve@chromium.org

[agrieve, 2015-10-16 01:02:49]

The CQ bit was checked by agrieve@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-10-16 01:03:11]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1410553004/90001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1410553004/90001

[agrieve, 2015-10-16 01:05:09]

On 2015/10/16 00:56:58, commit-bot: I haz the power wrote:
> Dry run: CQ is trying da patch. Follow status at
>  https://chromium-cq-status.appspot.com/patch-status/1410553004/70001
> View timeline at
>  https://chromium-cq-status.appspot.com/patch-timeline/1410553004/70001

John - please have a new look. Fixed the issue that failed on the waterfall:
DeviceUtils.ReadFile(as_root=True). It was depending on the file to be touched
as non-root so that when copied over it would stay world readable. I've added an
explicit chmod to address this.

Also found provision_devices.py was using it to write a file, so added an
explicit WriteFile there. 

Scanned through all usages reported by code search, so hopefully this'll do it!

[jbudorick, 2015-10-16 01:16:55]

lgtm

https://codereview.chromium.org/1410553004/diff/90001/build/android/devil/and...
File build/android/devil/android/device_utils.py (right):

https://codereview.chromium.org/1410553004/diff/90001/build/android/devil/and...
build/android/devil/android/device_utils.py:1439: cmd = 'SRC=%s DEST=%s;cp
"$SRC" "$DEST" && chmod 666 "$DEST"' % (
I'm going to have to mull over that Shrink function. We should be able to come
up with something general here...

[commit-bot: I haz the power, 2015-10-16 02:06:20]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-10-16 02:06:20]

Dry run: This issue passed the CQ dry run.

[agrieve, 2015-10-16 15:28:33]

The CQ bit was checked by agrieve@chromium.org

[commit-bot: I haz the power, 2015-10-16 15:29:18]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1410553004/90001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1410553004/90001

[commit-bot: I haz the power, 2015-10-16 15:34:16]

Committed patchset #3 (id:90001)

[commit-bot: I haz the power, 2015-10-16 15:34:53]

Patchset 3 (id:??) landed as
https://crrev.com/fc5b96fe6e0b196889a3aba6ba016b471e9cf510
Cr-Commit-Position: refs/heads/master@{#354516}