Allow startup with missing V8 snapshot file.

chrome/browser/chrome_content_browser_client.cc

 // Copyright (c) 2012 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 "chrome/browser/chrome_content_browser_client.h"
 
 #include <set>
 #include <utility>
 #include <vector>
 
@@ skipping 1150 matching lines @@
   }
   if (browser_command_line.HasSwitch(
       switches::kDisableOfflineAutoReloadVisibleOnly)) {
     return false;
   }
   return true;
 }
 
 }  // namespace
 
+// When Chrome is updated on non-Windows platforms, the new files (like
+// V8 natives and snapshot) can have the same names as the previous
+// versions. Since the renderers for an existing Chrome browser process
+// are likely not compatible with the new files, the browser keeps hold
+// of the old files using an open fd. This fd is passed to subprocesses
+// like renderers.  Here we add the flag to tell the subprocesses where
+// to find these file descriptors.
+void ChromeContentBrowserClient::AppendMappedFileCommandLineSwitches(
+    base::CommandLine* command_line) {
+#if defined(OS_POSIX) && !defined(OS_MACOSX)
+#if defined(V8_USE_EXTERNAL_STARTUP_DATA)
+  std::string process_type =
+      command_line->GetSwitchValueASCII(switches::kProcessType);
+  if (process_type != switches::kZygoteProcess) {
+    // We want to pass the natives by fd because after an update the file may
+    // be updated, but we want the newly launched renderers to get the old one,
+    // opened by the browser when it started.
+    DCHECK(natives_fd_exists());
+    command_line->AppendSwitch(::switches::kV8NativesPassedByFD);
+    if (snapshot_fd_exists())
+      command_line->AppendSwitch(::switches::kV8SnapshotPassedByFD);
+  }
+#endif  // V8_USE_EXTERNAL_STARTUP_DATA
+#endif  // OS_POSIX && !OS_MACOSX
+}
+
 void ChromeContentBrowserClient::AppendExtraCommandLineSwitches(
     base::CommandLine* command_line,
     int child_process_id) {
 #if defined(OS_MACOSX)
   scoped_ptr<metrics::ClientInfo> client_info =
       GoogleUpdateSettings::LoadMetricsClientInfo();
   if (client_info) {
     command_line->AppendSwitchASCII(switches::kMetricsClientID,
                                     client_info->client_id);
   }
@@ skipping 38 matching lines @@
   command_line->CopySwitchesFrom(browser_command_line, kChromeOSSwitches,
                                  arraysize(kChromeOSSwitches));
 
   // On Chrome OS need to pass primary user homedir (in multi-profiles session).
   base::FilePath homedir;
   PathService::Get(base::DIR_HOME, &homedir);
   command_line->AppendSwitchASCII(chromeos::switches::kHomedir,
                                   homedir.value().c_str());
 #endif
 
-#if defined(OS_POSIX) && !defined(OS_MACOSX)
-#if defined(V8_USE_EXTERNAL_STARTUP_DATA)
-  if (process_type != switches::kZygoteProcess) {
-    command_line->AppendSwitch(::switches::kV8NativesPassedByFD);
-    command_line->AppendSwitch(::switches::kV8SnapshotPassedByFD);
-  }
-#endif  // V8_USE_EXTERNAL_STARTUP_DATA
-#endif  // OS_POSIX && !OS_MACOSX
-
   if (process_type == switches::kRendererProcess) {
     content::RenderProcessHost* process =
         content::RenderProcessHost::FromID(child_process_id);
     Profile* profile =
         process ? Profile::FromBrowserContext(process->GetBrowserContext())
                 : NULL;
     for (size_t i = 0; i < extra_parts_.size(); ++i) {
       extra_parts_[i]->AppendExtraRendererCommandLineSwitches(
           command_line, process, profile);
     }
@@ skipping 970 matching lines @@
         browser_context, storage_partition_path, additional_backends);
   }
 }
 
 #if defined(OS_POSIX) && !defined(OS_MACOSX)
 void ChromeContentBrowserClient::GetAdditionalMappedFilesForChildProcess(
     const base::CommandLine& command_line,
     int child_process_id,
     FileDescriptorInfo* mappings) {
 #if defined(V8_USE_EXTERNAL_STARTUP_DATA)
-  if (v8_natives_fd_.get() == -1 || v8_snapshot_fd_.get() == -1) {
+  if (!natives_fd_exists()) {
     int v8_natives_fd = -1;
     int v8_snapshot_fd = -1;
     if (gin::V8Initializer::OpenV8FilesForChildProcesses(&v8_natives_fd,
                                                          &v8_snapshot_fd)) {
       v8_natives_fd_.reset(v8_natives_fd);
       v8_snapshot_fd_.reset(v8_snapshot_fd);
     }
   }
-  DCHECK(v8_natives_fd_.get() != -1 && v8_snapshot_fd_.get() != -1);
+  // V8 can't start up without the source of the natives, but it can
+  // start up (slower) without the snapshot.
+  DCHECK(natives_fd_exists());
   mappings->Share(kV8NativesDataDescriptor, v8_natives_fd_.get());
-  mappings->Share(kV8SnapshotDataDescriptor, v8_snapshot_fd_.get());
+  if (snapshot_fd_exists())
+    mappings->Share(kV8SnapshotDataDescriptor, v8_snapshot_fd_.get());
 #endif  // V8_USE_EXTERNAL_STARTUP_DATA
 
 #if defined(OS_ANDROID)
   base::FilePath data_path;
   PathService::Get(ui::DIR_RESOURCE_PAKS_ANDROID, &data_path);
   DCHECK(!data_path.empty());
 
   int flags = base::File::FLAG_OPEN | base::File::FLAG_READ;
   base::FilePath chrome_resources_pak =
       data_path.AppendASCII("chrome_100_percent.pak");
@@ skipping 196 matching lines @@
       switches::kDisableWebRtcEncryption,
     };
     to_command_line->CopySwitchesFrom(from_command_line,
                                       kWebRtcDevSwitchNames,
                                       arraysize(kWebRtcDevSwitchNames));
   }
 }
 #endif  // defined(ENABLE_WEBRTC)
 
 }  // namespace chrome