Make it possible to read CLD data from a file

chrome/browser/translate/translate_tab_helper.cc

Index: chrome/browser/translate/translate_tab_helper.cc
diff --git a/chrome/browser/translate/translate_tab_helper.cc b/chrome/browser/translate/translate_tab_helper.cc
index bae7a5984c1eafd9be8b712c9d2192326930bed0..86aeb0c561c8f4ba20ef67bf8f76766aa3f36edb 100644
--- a/chrome/browser/translate/translate_tab_helper.cc
+++ b/chrome/browser/translate/translate_tab_helper.cc
@@ -4,6 +4,8 @@
 
 #include "chrome/browser/translate/translate_tab_helper.h"
 
+#include "base/path_service.h"
+#include "base/platform_file.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/translate/translate_accept_languages_factory.h"
@@ -15,6 +17,7 @@
 #include "chrome/browser/ui/browser_window.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
 #include "chrome/browser/ui/translate/translate_bubble_factory.h"
+#include "chrome/common/chrome_paths.h"
 #include "chrome/common/pref_names.h"
 #include "chrome/common/render_messages.h"
 #include "components/translate/core/browser/page_translated_details.h"
@@ -22,6 +25,8 @@
 #include "components/translate/core/browser/translate_prefs.h"
 #include "components/translate/core/common/language_detection_details.h"
 #include "content/public/browser/notification_service.h"
+#include "content/public/browser/render_process_host.h"
+#include "content/public/browser/render_view_host.h"
 #include "content/public/browser/web_contents.h"
 
 DEFINE_WEB_CONTENTS_USER_DATA_KEY(TranslateTabHelper);
@@ -112,6 +117,7 @@ bool TranslateTabHelper::OnMessageReceived(const IPC::Message& message) {
     IPC_MESSAGE_HANDLER(ChromeViewHostMsg_TranslateLanguageDetermined,
                         OnLanguageDetermined)
     IPC_MESSAGE_HANDLER(ChromeViewHostMsg_PageTranslated, OnPageTranslated)
+    IPC_MESSAGE_HANDLER(ChromeViewHostMsg_NeedCLDData, OnCLDDataRequested)
     IPC_MESSAGE_UNHANDLED(handled = false)
   IPC_END_MESSAGE_MAP()
 
@@ -133,6 +139,59 @@ void TranslateTabHelper::WebContentsDestroyed(
   translate_manager_.reset();
 }
 
+// TODO(andrewhayden): It's annoying that during download of the data file,
+// multiple renderers may be calling this method repeatedly, but there's not
+// an obviously-better choice from a complexity standpoint: we have no idea
+// if or when the file will become available, and the check is cheap.
+void TranslateTabHelper::OnCLDDataRequested() {
+  static base::PlatformFile cached_platform_file = 0;
+  const int routing_id = GetWebContents()->GetRenderViewHost()->GetRoutingID();
+
+  // If we have cached the platform file, we reuse it. Else, we cache it now.
+  if (cached_platform_file == 0) {
+    // First, grab a reference to the user data directory
+    base::FilePath path;
+    if (!PathService::Get(chrome::DIR_USER_DATA, &path)) {
+        NOTREACHED();

[jochen (gone - plz use gerrit), 2014/03/12 13:08:27]

i don't think this if () { NOTREACHED(); } adds much value here

[Andrew Hayden (chromium.org), 2014/03/13 16:39:48]

Done.

+    }
+
+    // Now derive the name of the CLD data file that we are looking for.
+    path = path.Append(chrome::kCLDDataFilename);
+
+    // If the file exists, we can send an IPC-safe construct back to the
+    // renderer process immediately. If not (e.g., the file is being downloaded
+    // right now), then we will do nothing. It is up to the renderer process
+    // to call us again later.
+    if (!base::PathExists(path)) {
+      return;

[jochen (gone - plz use gerrit), 2014/03/12 13:08:27]

no { }

[Andrew Hayden (chromium.org), 2014/03/13 16:39:48]

Done.

+    }
+
+    // Attempt to open the file for reading.
+    int flags = base::PLATFORM_FILE_OPEN | base::PLATFORM_FILE_READ;
+    bool created = false;
+    base::PlatformFileError error;
+    cached_platform_file = base::CreatePlatformFile(
+        path, flags, &created, &error);
+    DCHECK(created == false);

[jochen (gone - plz use gerrit), 2014/03/12 13:08:27]

!created

[Andrew Hayden (chromium.org), 2014/03/13 16:39:48]

Done.

+    if (error != base::PLATFORM_FILE_OK) {
+      cached_platform_file = 0;
+      DCHECK(false) << "Failed to open CLD data file, error code=" << error;

[jochen (gone - plz use gerrit), 2014/03/12 13:08:27]

is it really necessary to crash here?

[Andrew Hayden (chromium.org), 2014/03/13 16:39:48]

No, it isn't. I just put a comment in the code instead. Thanks.

+      return;
+    }
+  }
+
+  // Get a handle to the renderer process for IPC.
+  base::ProcessHandle rendererProcessHandle =
+      GetWebContents()->GetRenderViewHost()->GetProcess()->GetHandle();
+  // Prepare a file handle for transit to that renderer process.
+  IPC::PlatformFileForTransit ipcPlatformFile = IPC::GetFileHandleForProcess(
+      cached_platform_file,
+      rendererProcessHandle,
+      false);
+  // Send the file handle to the renderer via IPC. We're done!
+  Send(new ChromeViewMsg_CLDDataAvailable(routing_id, ipcPlatformFile));
+}
+
 void TranslateTabHelper::OnLanguageDetermined(
     const LanguageDetectionDetails& details,
     bool page_needs_translation) {