Allow startup with missing V8 snapshot file.

content/shell/browser/shell_content_browser_client.cc

Index: content/shell/browser/shell_content_browser_client.cc
diff --git a/content/shell/browser/shell_content_browser_client.cc b/content/shell/browser/shell_content_browser_client.cc
index 4a2e95c26a0ef851819e97116967a9a2042f8656..c759b2101a0fbaaaf4816581a39e0416cb208082 100644
--- a/content/shell/browser/shell_content_browser_client.cc
+++ b/content/shell/browser/shell_content_browser_client.cc
@@ -214,8 +214,12 @@ void ShellContentBrowserClient::AppendExtraCommandLineSwitches(
   std::string process_type =
       command_line->GetSwitchValueASCII(switches::kProcessType);
   if (process_type != switches::kZygoteProcess) {
-    command_line->AppendSwitch(::switches::kV8NativesPassedByFD);
-    command_line->AppendSwitch(::switches::kV8SnapshotPassedByFD);
+    if (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
@@ -343,7 +347,7 @@ void ShellContentBrowserClient::GetAdditionalMappedFilesForChildProcess(
     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,
@@ -352,7 +356,9 @@ void ShellContentBrowserClient::GetAdditionalMappedFilesForChildProcess(
       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.

[rmcilroy, 2015/06/02 15:20:27]

Can you add this comment to all ContentBrowserClient subclasses please.

[Erik Corry Chromium.org, 2015/06/04 11:40:40]

Done.

+  DCHECK(natives_fd_exists());
   mappings->Share(kV8NativesDataDescriptor, v8_natives_fd_.get());
   mappings->Share(kV8SnapshotDataDescriptor, v8_snapshot_fd_.get());
 #endif  // V8_USE_EXTERNAL_STARTUP_DATA