Allow startup with missing V8 snapshot file.

chrome/browser/chrome_content_browser_client.cc

Index: chrome/browser/chrome_content_browser_client.cc
diff --git a/chrome/browser/chrome_content_browser_client.cc b/chrome/browser/chrome_content_browser_client.cc
index e07ea7aa1525c34b4ffab0b1a833072daa79498a..6d9a3303e016a1ea61316577f0ffc2d0585d7997 100644
--- a/chrome/browser/chrome_content_browser_client.cc
+++ b/chrome/browser/chrome_content_browser_client.cc
@@ -1229,8 +1229,12 @@ void ChromeContentBrowserClient::AppendExtraCommandLineSwitches(
 #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);
+    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
@@ -2225,7 +2229,7 @@ void ChromeContentBrowserClient::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,
@@ -2234,9 +2238,10 @@ void ChromeContentBrowserClient::GetAdditionalMappedFilesForChildProcess(
       v8_snapshot_fd_.reset(v8_snapshot_fd);
     }
   }
-  DCHECK(v8_natives_fd_.get() != -1 && v8_snapshot_fd_.get() != -1);
+  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)