Remember zoom on a per-host basis....

chrome/common/render_messages_internal.h

 // Copyright (c) 2009 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.
 
 // This header is meant to be included in multiple passes, hence no traditional
 // header guard.
 // See ipc_message_macros.h for explanation of the macros and passes.
 
 #include <map>
 #include <string>
 #include <vector>
 
 #include "build/build_config.h"
 
 #include "app/clipboard/clipboard.h"
 #include "app/gfx/native_widget_types.h"
 #include "base/file_path.h"
 #include "base/nullable_string16.h"
 #include "base/platform_file.h"
 #include "base/gfx/rect.h"
 #include "base/shared_memory.h"
 #include "base/values.h"
 #include "chrome/common/css_colors.h"
 #include "chrome/common/extensions/update_manifest.h"
 #include "chrome/common/nacl_types.h"
 #include "chrome/common/notification_type.h"
+#include "chrome/common/page_zoom.h"
 #include "chrome/common/transport_dib.h"
 #include "chrome/common/view_types.h"
 #include "ipc/ipc_channel_handle.h"
 #include "ipc/ipc_message.h"
 #include "ipc/ipc_message_macros.h"
 #include "ipc/ipc_platform_file.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "webkit/appcache/appcache_interfaces.h"
 #include "webkit/glue/dom_operations.h"
 #include "webkit/glue/webcursor.h"
@@ skipping 303 matching lines @@
                       string16 /* frame_xpath */,
                       string16 /* message */,
                       WebKit::WebConsoleMessage::Level /* message_level */)
 
   // RenderViewHostDelegate::RenderViewCreated method sends this message to a
   // new renderer to notify it that it will host developer tools UI and should
   // set up all neccessary bindings and create DevToolsClient instance that
   // will handle communication with inspected page DevToolsAgent.
   IPC_MESSAGE_ROUTED0(ViewMsg_SetupDevToolsClient)
 
-  // Change the zoom level in the renderer.
+  // Change the zoom level for the current main frame.  If the level actually
+  // changes, a ViewHostMsg_DidZoomHost message will be sent back to the browser
+  // telling it what host got zoomed and what its current zoom level is.
   IPC_MESSAGE_ROUTED1(ViewMsg_Zoom,
-                      int /* One of PageZoom::Function */)
+                      PageZoom::Function /* function */)
+
+  // Set the zoom level for a particular hostname that the renderer is in the
+  // process of loading.  This will be stored, to be used if the load commits
+  // and ignored otherwise.
+  IPC_MESSAGE_ROUTED2(ViewMsg_SetZoomLevelForLoadingHost,
+                      std::string /* host */,
+                      int /* zoom_level */)
+
+  // Set the zoom level for a particular hostname, so all render views
+  // displaying this host can update their zoom levels to match.
+  IPC_MESSAGE_CONTROL2(ViewMsg_SetZoomLevelForCurrentHost,
+                       std::string /* host */,
+                       int /* zoom_level */)
 
   // Change encoding of page in the renderer.
   IPC_MESSAGE_ROUTED1(ViewMsg_SetPageEncoding,
                       std::string /*new encoding name*/)
 
   // Reset encoding of page in the renderer back to default.
   IPC_MESSAGE_ROUTED0(ViewMsg_ResetPageEncodingToDefault)
 
   // Requests the renderer to reserve a range of page ids.
   IPC_MESSAGE_ROUTED1(ViewMsg_ReservePageIDRange,
@@ skipping 1181 matching lines @@
   // Sent by the renderer process to acknowledge receipt of a
   // DownloadProgress message.
   IPC_MESSAGE_ROUTED1(ViewHostMsg_DownloadProgress_ACK,
                       int /* request_id */)
 
   // Sent by the renderer process to acknowledge receipt of a
   // UploadProgress message.
   IPC_MESSAGE_ROUTED1(ViewHostMsg_UploadProgress_ACK,
                       int /* request_id */)
 
+  // Sent when the renderer changes the zoom level for a particular host, so the
+  // browser can update its records.
+  IPC_MESSAGE_CONTROL2(ViewHostMsg_DidZoomHost,
+                       std::string /* host */,
+                       int /* zoom_level */)
+
 #if defined(OS_WIN)
   // Duplicates a shared memory handle from the renderer to the browser. Then
   // the renderer can flush the handle.
   IPC_SYNC_MESSAGE_ROUTED1_1(ViewHostMsg_DuplicateSection,
                              base::SharedMemoryHandle /* renderer handle */,
                              base::SharedMemoryHandle /* browser handle */)
 #endif
 
 #if defined(OS_LINUX)
   // Asks the browser create a temporary file for the renderer to fill
@@ skipping 471 matching lines @@
                               string16 /* word */,
                               int /* document tag */,
                               bool /* correct */)
 
   IPC_SYNC_MESSAGE_CONTROL1_1(
       ViewHostMsg_SpellChecker_PlatformFillSuggestionList,
       string16 /* word */,
       std::vector<string16> /* suggestions */)
 
 IPC_END_MESSAGES(ViewHost)