Create a Lite Page bit for previews and fallback to Lo-Fi

content/common/frame_messages.h

 // Copyright 2013 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.
 
 // IPC messages for interacting with frames.
 // Multiply-included message file, hence no include guard.
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 88 matching lines @@
                           blink::WebContextMenuData::InputFieldTypeLast)
 IPC_ENUM_TRAITS_MAX_VALUE(blink::WebFocusType, blink::WebFocusTypeLast)
 IPC_ENUM_TRAITS_MAX_VALUE(blink::WebFrameOwnerProperties::ScrollingMode,
                           blink::WebFrameOwnerProperties::ScrollingMode::Last)
 IPC_ENUM_TRAITS_MAX_VALUE(content::StopFindAction,
                           content::STOP_FIND_ACTION_LAST)
 IPC_ENUM_TRAITS(blink::WebSandboxFlags)  // Bitmask.
 IPC_ENUM_TRAITS_MAX_VALUE(blink::WebTreeScopeType,
                           blink::WebTreeScopeType::Last)
 IPC_ENUM_TRAITS_MAX_VALUE(ui::MenuSourceType, ui::MENU_SOURCE_TYPE_LAST)
-IPC_ENUM_TRAITS_MIN_MAX_VALUE(content::PreviewsState,
-                              content::PREVIEWS_UNSPECIFIED,
-                              content::PREVIEWS_STATE_LAST)
 IPC_ENUM_TRAITS_MAX_VALUE(content::FileChooserParams::Mode,
                           content::FileChooserParams::Save)
 IPC_ENUM_TRAITS_MAX_VALUE(content::CSPDirective::Name,
                           content::CSPDirective::NameLast)
 IPC_ENUM_TRAITS_MAX_VALUE(blink::WebFeaturePolicyFeature,
                           blink::WebFeaturePolicyFeature::LAST_FEATURE)
 
 IPC_STRUCT_TRAITS_BEGIN(blink::WebFindOptions)
   IPC_STRUCT_TRAITS_MEMBER(forward)
   IPC_STRUCT_TRAITS_MEMBER(matchCase)
@@ skipping 1489 matching lines @@
 // nearest find result in the sending frame.
 IPC_MESSAGE_ROUTED2(FrameHostMsg_GetNearestFindResult_Reply,
                     int /* nfr_request_id */,
                     float /* distance */)
 #endif
 
 // Adding a new message? Stick to the sort order above: first platform
 // independent FrameMsg, then ifdefs for platform specific FrameMsg, then
 // platform independent FrameHostMsg, then ifdefs for platform specific
 // FrameHostMsg.