Use a valid /prefetch argument when launching a process.

chrome/app/chrome_exe_main_win.cc

Index: chrome/app/chrome_exe_main_win.cc
diff --git a/chrome/app/chrome_exe_main_win.cc b/chrome/app/chrome_exe_main_win.cc
index 2102ae1676d1a40c73f609b3226d11a70e7c7970..089ca1280dd418d1a16b0c454884e4823a4a378d 100644
--- a/chrome/app/chrome_exe_main_win.cc
+++ b/chrome/app/chrome_exe_main_win.cc
@@ -17,6 +17,8 @@
 #include "base/lazy_instance.h"
 #include "base/logging.h"
 #include "base/macros.h"
+#include "base/strings/string16.h"
+#include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/time/time.h"
 #include "base/win/windows_version.h"
@@ -26,10 +28,12 @@
 #include "chrome/browser/policy/policy_path_parser.h"
 #include "chrome/common/chrome_paths_internal.h"
 #include "chrome/common/chrome_switches.h"
+#include "chrome/installer/util/browser_distribution.h"
 #include "chrome_elf/chrome_elf_main.h"
 #include "components/crash/content/app/crash_reporter_client.h"
 #include "components/crash/content/app/crashpad.h"
 #include "components/startup_metric_utils/browser/startup_metric_utils.h"
+#include "components/startup_metric_utils/common/pre_read_field_trial_utils_win.h"
 #include "content/public/common/content_switches.h"
 #include "content/public/common/result_codes.h"
 #include "third_party/crashpad/crashpad/handler/handler_main.h"
@@ -152,15 +156,39 @@ int RunAsCrashpadHandler(const base::CommandLine& command_line) {
   scoped_ptr<char* []> argv_as_utf8(new char*[argv.size() + 1]);
   std::vector<std::string> storage;
   storage.reserve(argv.size());
+
+  size_t arg_append_index = 0;
   for (size_t i = 0; i < argv.size(); ++i) {
+    // Remove arguments starting with '/' as they are not supported by crashpad.
+    if (!argv[i].empty() && argv[i].front() == L'/')
+      continue;
+
     storage.push_back(base::UTF16ToUTF8(argv[i]));
-    argv_as_utf8[i] = &storage[i][0];
+    argv_as_utf8[arg_append_index] = &storage[arg_append_index][0];
+    ++arg_append_index;
   }
-  argv_as_utf8[argv.size()] = nullptr;
-  return crashpad::HandlerMain(static_cast<int>(argv.size()),
+  argv_as_utf8[arg_append_index] = nullptr;
+
+  return crashpad::HandlerMain(static_cast<int>(storage.size()),
                                argv_as_utf8.get());
 }
 
+// Returns true if |command_line| contains a /prefetch:# argument where # is in
+// [1, 8].
+bool HasValidWindowsPrefetchArgument(const base::CommandLine& command_line) {
+  const base::char16 kPrefetchArgumentPrefix[] = L"/prefetch:";
+
+  for (const auto& arg : command_line.argv()) {
+    if (arg.size() == arraysize(kPrefetchArgumentPrefix) &&
+        base::StartsWith(arg, kPrefetchArgumentPrefix,
+                         base::CompareCase::SENSITIVE)) {
+      return arg[arraysize(kPrefetchArgumentPrefix) - 1] >= L'1' &&
+             arg[arraysize(kPrefetchArgumentPrefix) - 1] <= L'8';
+    }
+  }
+  return false;
+}
+
 }  // namespace
 
 // This helper is looked up in the browser to retrieve the crash reports. See
@@ -183,10 +211,22 @@ int main() {
 #endif
   // Initialize the CommandLine singleton from the environment.
   base::CommandLine::Init(0, nullptr);
+  const base::CommandLine* command_line =
+      base::CommandLine::ForCurrentProcess();
+
+  const std::string process_type =
+      command_line->GetSwitchValueASCII(switches::kProcessType);
+
+  startup_metric_utils::InitializePreReadOptions(
+      BrowserDistribution::GetDistribution()->GetRegistryPath());
 
-  std::string process_type =
-      base::CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
-          switches::kProcessType);
+  // Confirm that an explicit prefetch profile is used for all process types
+  // except for the browser process. Any new process type will have to assign
+  // itself a prefetch id. See kPrefetchArgument* constants in
+  // content_switches.cc for details.
+  DCHECK(!startup_metric_utils::GetPreReadOptions().use_prefetch_argument ||
+         process_type.empty() ||
+         HasValidWindowsPrefetchArgument(*command_line));
 
   if (process_type == switches::kCrashpadHandler)
     return RunAsCrashpadHandler(*base::CommandLine::ForCurrentProcess());
@@ -210,7 +250,7 @@ int main() {
   if (base::win::GetVersion() >= base::win::VERSION_WIN7)
     EnableHighDPISupport();
 
-  if (AttemptFastNotify(*base::CommandLine::ForCurrentProcess()))
+  if (AttemptFastNotify(*command_line))
     return 0;
 
   // Load and launch the chrome dll. *Everything* happens inside.