Ignore the default zoom level for the PDF extension and print preview.

extensions/browser/guest_view/mime_handler_view/mime_handler_view_guest.cc

 // Copyright 2014 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.
 
 #include "extensions/browser/guest_view/mime_handler_view/mime_handler_view_guest.h"
 
 #include "base/strings/stringprintf.h"
 #include "content/public/browser/browser_thread.h"
+#include "content/public/browser/host_zoom_map.h"
 #include "content/public/browser/render_process_host.h"
 #include "content/public/browser/stream_handle.h"
 #include "content/public/browser/stream_info.h"
 #include "content/public/common/service_registry.h"
 #include "content/public/common/url_constants.h"
 #include "extensions/browser/api/extensions_api_client.h"
 #include "extensions/browser/api/mime_handler_private/mime_handler_private.h"
 #include "extensions/browser/extension_registry.h"
 #include "extensions/browser/guest_view/mime_handler_view/mime_handler_stream_manager.h"
 #include "extensions/browser/guest_view/mime_handler_view/mime_handler_view_constants.h"
 #include "extensions/browser/guest_view/mime_handler_view/mime_handler_view_guest_delegate.h"
 #include "extensions/browser/process_manager.h"
+#include "extensions/common/constants.h"
 #include "extensions/common/extension_messages.h"
 #include "extensions/common/guest_view/guest_view_constants.h"
 #include "extensions/strings/grit/extensions_strings.h"
 #include "ipc/ipc_message_macros.h"
 #include "net/base/url_util.h"
 
 using content::WebContents;
 
 namespace extensions {
 
@@ skipping 85 matching lines @@
     LOG(ERROR) << "Extension for mime_type not found, mime_type = "
                << stream_->stream_info()->mime_type;
     callback.Run(nullptr);
     return;
   }
 
   // Use the mime handler extension's SiteInstance to create the guest so it
   // goes under the same process as the extension.
   ProcessManager* process_manager = ProcessManager::Get(browser_context());
   content::SiteInstance* guest_site_instance =
-      process_manager->GetSiteInstanceForURL(
-          Extension::GetBaseURLFromExtensionId(GetOwnerSiteURL().host()));
+      process_manager->GetSiteInstanceForURL(stream_->handler_url());
+
+  // Clear the zoom level for the mime handler extension. The extension is
+  // responsible for managing its own zoom. This is necessary for OOP PDF, as
+  // otherwise the UI is zoomed and the calculations to determine the PDF size
+  // mix zoomed and unzoomed units.
+  content::HostZoomMap::Get(guest_site_instance)
+      ->SetZoomLevelForHostAndScheme(kExtensionScheme, stream_->extension_id(),
+                                     0);
 
   WebContents::CreateParams params(browser_context(), guest_site_instance);
   params.guest_delegate = this;
   callback.Run(WebContents::Create(params));
 }
 
 void MimeHandlerViewGuest::DidAttachToEmbedder() {
   web_contents()->GetController().LoadURL(
       stream_->handler_url(), content::Referrer(),
       ui::PAGE_TRANSITION_AUTO_TOPLEVEL, std::string());
@@ skipping 88 matching lines @@
 
 void MimeHandlerViewGuest::OnRequest(
     const ExtensionHostMsg_Request_Params& params) {
   if (extension_function_dispatcher_) {
     extension_function_dispatcher_->Dispatch(
         params, web_contents()->GetRenderViewHost());
   }
 }
 
 }  // namespace extensions