Remove methods that modify cookie storage at runtime (see issue #2622).

This change removes cookie and request handler functionality that will not
supported by the NetworkService. Specifically, it is no longer possible to
change cookie storage locations at runime by returning a different
CefCookieManager for an already initialized CefRequestContext. After this change
you will need to use a separate CefRequestContext when creating a CefBrowser if
you require separate cookie storage.

The following methods have been removed:
- CefCookieManager::CreateManager
- CefCookieManager::GetBlockingManager
- CefCookieManager::SetStoragePath
- CefRequestContextHandler::GetCookieManager

The following methods have been renamed:
- CefRequestContext::GetDefaultCookieManager to GetCookieManager.

This change substantially simplifies the network implementation in CEF because
it is no longer necessary to proxy objects that are normally owned by Chromium.
Chromium patches that are no longer necessary will be removed as a follow-up
commit.

To test: Verify that `ceftests --gtest_filter=-PluginTest.*` pass with
NetworkService disabled. Plugin tests will be fixed in a follow-up commit.

tests/shared/common/client_switches.cc

@@ -30,7 +30,6 @@ const char kExternalBeginFrameEnabled[] = "external-begin-frame-enabled";
 const char kMouseCursorChangeDisabled[] = "mouse-cursor-change-disabled";
 const char kRequestContextPerBrowser[] = "request-context-per-browser";
 const char kRequestContextSharedCache[] = "request-context-shared-cache";
-const char kRequestContextBlockCookies[] = "request-context-block-cookies";
 const char kBackgroundColor[] = "background-color";
 const char kEnableGPU[] = "enable-gpu";
 const char kFilterURL[] = "filter-url";

tests/shared/common/client_switches.h

@@ -24,7 +24,6 @@ extern const char kExternalBeginFrameEnabled[];
 extern const char kMouseCursorChangeDisabled[];
 extern const char kRequestContextPerBrowser[];
 extern const char kRequestContextSharedCache[];
-extern const char kRequestContextBlockCookies[];
 extern const char kBackgroundColor[];
 extern const char kEnableGPU[];
 extern const char kFilterURL[];