Move extension unpack intermediate dir to Extensions/Temp

Move extension unpack intermediate dir to Extensions/Temp

This speeds up extension installation on Chrome OS by about 20%.  On Chrome OS
the USER_DATA_DIR is in /home/chronos, which is a different file system than
/home/chronos/user where the Extensions directory lives. Thus an attempt to
rename() an extension into place ends up being a recursive directory copy,
which is both non-atomic and slow.

Also add code to clean up the intermediate directory during extension garbage
collection, which might have lead to leaked files in the old code if Chrome
crashed during extension install.

Removed DIR_USER_DATA_TEMP as the extension install code was the only user.

Just use a temp directory for this during tests so we don't have to worry
about profile creation.

BUG=155994
TEST=Manual testing of extension install speed on Chrome OS, unit_tests ExtensionFromWebApp.* ExtensionFromUserScript.* SandboxedUnpackerTest.*

TBR=sky@chromium.org for removing an unused constant from chrome/common/chrome_paths.h


Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=162880

[James Cook, 2012-10-18 18:23:28]

Aaron, PTAL. This is the directory move we chatted about. It touches a bunch of
files because I need to pass the Profile/Extensions path down into
chrome/common, which doesn't know about profiles. The core change is at the
bottom of extension_file_util.cc.

[Aaron Boodman, 2012-10-18 21:11:12]

Cool change. Please make the naming changes consistently throughout.

http://codereview.chromium.org/11198067/diff/7002/chrome/browser/chromeos/kio...
File chrome/browser/chromeos/kiosk_mode/kiosk_mode_screensaver.cc (right):

http://codereview.chromium.org/11198067/diff/7002/chrome/browser/chromeos/kio...
chrome/browser/chromeos/kiosk_mode/kiosk_mode_screensaver.cc:150: FilePath
all_extensions_dir =
kinda funny name. extensions_dir? extensions_install_dir?

http://codereview.chromium.org/11198067/diff/7002/chrome/browser/extensions/c...
File chrome/browser/extensions/convert_user_script.cc (right):

http://codereview.chromium.org/11198067/diff/7002/chrome/browser/extensions/c...
chrome/browser/extensions/convert_user_script.cc:54:
extension_file_util::GetExtensionsTempDir(all_extensions_dir);
GetInstallTempDir? GetTempInstallDir?

[James Cook, 2012-10-18 21:43:54]

Aaron, PTAL.  I standardized on "extensions_dir" and GetInstallTempDir().

[Aaron Boodman, 2012-10-18 22:23:14]

lgtm, good change

[commit-bot: I haz the power, 2012-10-18 22:45:10]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/jamescook@chromium.org/11198067/5006

[commit-bot: I haz the power, 2012-10-19 01:16:36]

Change committed as 162880