Enable plugin layout tests that now pass with the network service after r552775.

Bug: 764474
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_mojo
Change-Id: I5816500cce7477784e948636e5f5f8a5b48c1062
Reviewed-on: https://chromium-review.googlesource.com/1028976Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Commit-Queue: John Abd-El-Malek <jam@chromium.org>
Cr-Commit-Position: refs/heads/master@{#553854}

third_party/WebKit/LayoutTests/FlagExpectations/enable-features=NetworkService

@@ -41,17 +41,6 @@ Bug(none) http/tests/security/mixedContent/filesystem-url-in-iframe.html [ Failu
 # Cross-Origin Read Blocking is not implemented.
 crbug.com/792546 http/tests/inspector-protocol/network/block_cross_site_document_load.js [ Failure ]
 
-# Plugin throttle is not implemented.
-crbug.com/764474 http/tests/security/contentSecurityPolicy/object-src-url-allowed.html [ Failure ]
-crbug.com/764474 http/tests/security/contentSecurityPolicy/1.1/plugintypes-affects-cross-site-child-disallowed.html [ Failure ]
-crbug.com/764474 http/tests/security/contentSecurityPolicy/object-src-does-not-affect-child.html [ Failure ]
-crbug.com/764474 fast/frames/iframe-plugin-load-remove-document-crash.html [ Failure ]
-crbug.com/764474 http/tests/security/contentSecurityPolicy/plugin-in-iframe-with-csp.html [ Failure ]
-crbug.com/764474 http/tests/security/contentSecurityPolicy/1.1/plugintypes-affects-child.html [ Failure ]
-crbug.com/764474 http/tests/security/contentSecurityPolicy/1.1/plugintypes-affects-cross-site-child-allowed.html [ Failure ]
-crbug.com/764474 fast/loader/reload-zero-byte-plugin.html [ Failure ]
-crbug.com/764474 plugins/plugin-document-back-forward.html [ Crash Failure Timeout ]
-
 crbug.com/816556 external/wpt/html/semantics/text-level-semantics/the-a-element/a-download-click-404.html [ Failure ]
 crbug.com/829721 external/wpt/html/semantics/embedded-content/the-area-element/area-download-click.html [ Crash ]
 crbug.com/829721 external/wpt/html/semantics/text-level-semantics/the-a-element/a-download-click.html [ Crash ]