Revert of Always preload all tokens before parsing (https://codereview.chromium.org/302063002/)

Reason for revert:
This change breaks:
org.chromium.android_webview.test.AwSettingsTest#testBlockNetworkImagesDoesNotBlockDataUrlImage

Probably because it pre-loads images when "automatically load images" is disabled on Android.

See
http://build.chromium.org/p/tryserver.chromium/builders/android_dbg_triggered_tests/builds/159696/steps/androidwebview_instrumentation_tests/logs/stdio

Original issue's description:
> Always preload all tokens before parsing
> 
> This change is in preparation for re-writing the path
> through which tokens are handled on the main thread
> to allow them to be batched and deferred until more
> important work is done:
> https://codereview.chromium.org/258013009/
> 
> Currently the threaded parser uses the main thread's
> MessageQueue as its work-queue and we'll commonly
> queue 10 chunks of work in the main thread MessageQueue
> even if the first chunk takes a long time we'll still have to
> process the next 9 before we can do more important things
> like put up a frame because we don't have a separate
> queue for parser work.  258013009 will fix that.
> 
> http/tests/security/script-crossorigin-loads-correctly-credentials-2.html
> originally started failing with this change and it
> turns out that always-preloading found a real bug
> in CORS handling with preloads. The ResourceFetcher
> was incorrectly always reusing an in-flight preload
> request, even if the CORS state didn't match. Nate
> helped me re-order the calls in requestResource to fix it.
> 
> This change also discovered 2 other bugs in the preloader.
> 1. a preload request != LinkPrefect request
> and one will cancel the other. crbug.com/379893
> 2. The preloader has no concept of script type and will
> blindly issue preloads for all <script href> regardless
> of <script type>.  I decided this didn't matter in practice.
> Making the <script type> handling threadsafe isn't
> worth the trouble.
> 
> I would anticipate that this change might make some
> speed-index scores better (we'll now be preloading
> all tokens slightly sooner, especially those
> which are in the same chunk as a long inline
> script block for instance), but may make non-network
> PLT scores lower (due to extra mallocs required
> to process every chunk since more loads will
> be preloaded just before their actually loaded).
> 
> BUG=356292
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=175427

TBR=tonyg@chromium.org,japhet@chromium.org,eseidel@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=356292

Review URL: https://codereview.chromium.org/317703005

git-svn-id: svn://svn.chromium.org/blink/trunk@175512 bbb929c8-8fbe-4397-9dbb-9b2b20218538