Remove PluginLoadObserver and related logic, it was only used for NPAPI.

content/content_shell.gypi

 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 {
   'variables': {
     'content_shell_product_name': 'Content Shell',
     # The "19" is so that sites that sniff for version think that this is
     # something reasonably current; the "77.34.5" is a hint that this isn't a
     # standard Chrome.
@@ skipping 557 matching lines @@
     {
       'target_name': 'test_netscape_plugin',
       'type': 'loadable_module',
       'sources': [
         'shell/tools/plugin/PluginObject.cpp',
         'shell/tools/plugin/PluginObject.h',
         'shell/tools/plugin/PluginObjectMac.mm',
         'shell/tools/plugin/PluginTest.cpp',
         'shell/tools/plugin/PluginTest.h',
         'shell/tools/plugin/TestObject.cpp',
-        'shell/tools/plugin/Tests/DocumentOpenInDestroyStream.cpp',
         'shell/tools/plugin/Tests/EvaluateJSAfterRemovingPluginElement.cpp',
         'shell/tools/plugin/Tests/FormValue.cpp',
-        'shell/tools/plugin/Tests/GetURLNotifyWithURLThatFailsToLoad.cpp',
-        'shell/tools/plugin/Tests/GetURLWithJavaScriptURL.cpp',
-        'shell/tools/plugin/Tests/GetURLWithJavaScriptURLDestroyingPlugin.cpp',
         'shell/tools/plugin/Tests/GetUserAgentWithNullNPPFromNPPNew.cpp',
         'shell/tools/plugin/Tests/LeakWindowScriptableObject.cpp',
         'shell/tools/plugin/Tests/LogNPPSetWindow.cpp',
         'shell/tools/plugin/Tests/NPDeallocateCalledBeforeNPShutdown.cpp',
         'shell/tools/plugin/Tests/NPPNewFails.cpp',
         'shell/tools/plugin/Tests/NPRuntimeCallsWithNullNPP.cpp',
         'shell/tools/plugin/Tests/NPRuntimeObjectFromDestroyedPlugin.cpp',
         'shell/tools/plugin/Tests/NPRuntimeRemoveProperty.cpp',
         'shell/tools/plugin/Tests/NullNPPGetValuePointer.cpp',
         'shell/tools/plugin/Tests/PassDifferentNPPStruct.cpp',
@@ skipping 408 matching lines @@
                 '--input_symbol', '<(PRODUCT_DIR)/content_shell.exe.pdb',
                 '--destination_dir', '<(dest_dir)',
               ],
             },
           ],
         },
       ],
     }],  # OS=="win" and fastbuild==0 and target_arch=="ia32"
   ]
 }