Revert of Make start/stop loading notifications per-frame

Revert of Make start/stop loading notifications per-frame (https://codereview.chromium.org/183793002/)

Reason for revert:
Possibly causing content_browsertests EndToEnd to fail.

See: http://build.chromium.org/p/chromium.webkit/builders/Linux%20Tests%20%28dbg%29/builds/2095/steps/content_browsertests/logs/stdio

Output:
[20917:20917:0327/122353:3268961829:INFO:CONSOLE(0)] "Uncaught TypeError: Cannot convert undefined or null to object", source: http://127.0.0.1:34379/files/web_ui_mojo.html (0)
[20917:20917:0327/122353:3269022437:INFO:CONSOLE(28)] "Uncaught TypeError: undefined is not a function", source: http://127.0.0.1:34379/files/web_ui_mojo.js (28)
BrowserTestBase signal handler received SIGTERM. Backtrace:
#0 0x000000a593be base::debug::StackTrace::StackTrace()
#1 0x000002bfc17b content::(anonymous namespace)::DumpStackTraceSignalHandler()
#2 0x7f9c3e4ab4a0 <unknown>
#3 0x7f9c3e55da43 __poll
#4 0x7f9c42aabff6 <unknown>
#5 0x7f9c42aac124 g_main_context_iteration
#6 0x000000aaaf5f base::MessagePumpGlib::RunWithDispatcher()
#7 0x000000a8e802 base::RunLoop::Run()
#8 0x00000058256e content::(anonymous namespace)::WebUIMojoTest_EndToEnd_Test::RunTestOnMainThread()

Original issue's description:
> Make start/stop loading notifications per-frame
> 
> Also, make ProgressTracker a frame-level concept rather than a page-level concept and merge it with FrameLoader's FrameProgressTracker helper. Send per-frame progress change notifications accordingly.
> 
> This depends on https://codereview.chromium.org/180113003/ landing in chromium.
> 
> BUG=347643
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=170192

TBR=abarth@chromium.org,japhet@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=347643
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=170218

[enne (OOO), 2014-03-27 23:00:29]

Created Revert of Make start/stop loading notifications per-frame

[commit-bot: I haz the power, 2014-03-27 23:00:34]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/enne@chromium.org/215533004/1

[commit-bot: I haz the power, 2014-03-27 23:01:42]

Change committed as 170218

[tkent, 2014-03-28 02:15:54]

A revert of this CL has been created in
https://codereview.chromium.org/216083002/ by tkent@chromium.org.

The reason for reverting is: r170192 was not a culprit.
.