Revert "AW: enable PlzNavigate via CLI switch"

This reverts commit 267e445.

Reason for revert: We've already seen lots of breakages with PlzNavigate

Original change's description:
> AW: enable PlzNavigate via CLI switch
> 
> This CL enables PlzNavigate (browser side navigation) by default for
> WebView only. This is to try out the new code path before launching at
> 100% for all of chrome.
> 
> [email protected]
> 
> (cherry picked from commit dbc2bb9)
> 
> Bug: 765250
> Test: Manual
> Change-Id: Iff2d0585e11075e71fe196df47503d950e2b26b3
> Reviewed-on: https://chromium-review.googlesource.com/667502
> Reviewed-by: Selim Gurun <[email protected]>
> Commit-Queue: Nate Fischer <[email protected]>
> Cr-Original-Commit-Position: refs/heads/master@{#502121}
> Reviewed-on: https://chromium-review.googlesource.com/671187
> Reviewed-by: Nate Fischer <[email protected]>
> Cr-Commit-Position: refs/branch-heads/3202@{crosswalk-project#300}
> Cr-Branched-From: fa6a5d8-refs/heads/master@{#499098}

[email protected],[email protected]

Change-Id: I173db64902172655a72161a244f3923c9c9ef196
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 765250
Reviewed-on: https://chromium-review.googlesource.com/672156
Reviewed-by: Nate Fischer <[email protected]>
Cr-Commit-Position: refs/branch-heads/3202@{crosswalk-project#316}
Cr-Branched-From: fa6a5d8-refs/heads/master@{#499098}

Author: ntfschr-chromium

android_webview/lib/aw_main_delegate.cc

@@ -109,12 +109,6 @@ bool AwMainDelegate::BasicStartupComplete(int* exit_code) {
   // metadata and controls.
   cl->AppendSwitch(switches::kDisableMediaSessionAPI);
 
-  // Enable PlzNavigate (browser-side navigation) by default for WebView before
-  // launch.
-  // TODO(ntfschr): remove this once PlzNavigate is enabled by default on trunk
-  // (crbug/765250).
-  cl->AppendSwitch(switches::kEnableBrowserSideNavigation);
-
 #if defined(V8_USE_EXTERNAL_STARTUP_DATA)
   if (cl->GetSwitchValueASCII(switches::kProcessType).empty()) {
     // Browser process (no type specified).