Re-order PNaCl startup events to start pexe fetch early and set indicator.

Start the pexe fetch early so that component updater can
see the URL request and intercept it. Do this before
checking that the compiler files actually exist, CU is
what ensures the compiler files exist.

For now, we set a "Accept: application/x-pnacl, */*".
Accept is usually used when there are alternative response
types, but the alternatives may take longer to ratify:

Alternatives:
- Modify the webkit/common/resource_type.h enum.  I
think because the PPAPI url loader proxies to Webkit's
WebURLRequest, so we'd have to change
WebKit/Source/platform/network/ResourceRequest.h as well,
and that seems a little risky to finish before M32 branch.
- Use a different header like "Pragma: x-pnacl-request"?
- ???

BUG=107438

Review URL: https://codereview.chromium.org/25869003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@231163 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 231163
Add option to download reference build from internal storage.

The Google storage is not always up-to-date with official build. This CL
downloads official builds by default from internal storage (requires corp)
net. 
Added --gs option to download from gs://.

BUG=302065
NOTRY=true

Review URL: https://codereview.chromium.org/33353002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@231165 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 231165