Revert of [Merge M49] Pre-read chrome_child.dll in the browser process. (patchset #1 id:1 of https://codereview.chromium.org/1729923002/ )

Reason for revert:
Doesn't compile.

Original issue's description:
> [Merge M49] Pre-read chrome_child.dll in the browser process.
>
> Add an option to the PreRead field trial to pre-read chrome_child.dll
> in the browser process rather than in child processes.
>
> This is expected to reduce PLT.PT_RequestToFinish.
>
> BUG=547794
>
> Review URL: https://codereview.chromium.org/1661503002
>
> Cr-Commit-Position: refs/heads/master@{#373867}
> (cherry picked from commit 015d4424a950809b8ece3cd840f6327de55d9a98)
>
> Conflicts:
> 	chrome/app/main_dll_loader_win.cc
>
> TBR=gab@chromium.org
>
> Committed: https://chromium.googlesource.com/chromium/src/+/57a792aaa69f38c0ef068c70ff3dbd3e285abf68

TBR=gab@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=547794

Review URL: https://codereview.chromium.org/1727183002

Cr-Commit-Position: refs/branch-heads/2623@{#497}
Cr-Branched-From: 92d77538a86529ca35f9220bd3cd512cbea1f086-refs/heads/master@{#369907}

2 files changed, 5 insertions, 20 deletions

diff --git a/components/startup_metric_utils/common/pre_read_field_trial_utils_win.cc b/components/startup_metric_utils/common/pre_read_field_trial_utils_win.cc
index 5778d02..229d402 100644
--- a/components/startup_metric_utils/common/pre_read_field_trial_utils_win.cc
+++ b/components/startup_metric_utils/common/pre_read_field_trial_utils_win.cc
@@ -5,7 +5,6 @@
 #include "components/startup_metric_utils/common/pre_read_field_trial_utils_win.h"
 
 #include "base/callback.h"
-#include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/metrics/field_trial.h"
 #include "base/strings/string_util.h"
@@ -35,15 +34,13 @@ const base::char16 kHighPriorityVariationName[] = L"HighPriority";
 const base::char16 kPrefetchVirtualMemoryVariationName[] =
     L"PrefetchVirtualMemory";
 const base::char16 kNoPrefetchArgumentVariationName[] = L"NoPrefetchArgument";
-const base::char16 kPreReadChromeChildInBrowser[] =
-    L"PreReadChromeChildInBrowser";
 
 // Registry key in which the PreRead field trial group is stored.
 const base::char16 kPreReadFieldTrialRegistryKey[] = L"\\PreReadFieldTrial";
 
 // Pre-read options to use for the current process. This is initialized by
 // InitializePreReadOptions().
-PreReadOptions g_pre_read_options = {};
+PreReadOptions g_pre_read_options = {false, false, false, false};
 
 // Returns the registry path in which the PreRead group is stored.
 base::string16 GetPreReadRegistryPath(
@@ -62,12 +59,6 @@ bool ReadBool(const base::win::RegKey& key, const base::char16* name) {
 void InitializePreReadOptions(const base::string16& product_registry_path) {
   DCHECK(!product_registry_path.empty());
 
-#if DCHECK_IS_ON()
-  static bool initialized = false;
-  DCHECK(!initialized);
-  initialized = true;
-#endif  // DCHECK_IS_ON()
-
   // Open the PreRead field trial's registry key.
   const base::string16 registry_path =
       GetPreReadRegistryPath(product_registry_path);
@@ -81,8 +72,6 @@ void InitializePreReadOptions(const base::string16& product_registry_path) {
       ReadBool(key, kPrefetchVirtualMemoryVariationName);
   g_pre_read_options.use_prefetch_argument =
       !ReadBool(key, kNoPrefetchArgumentVariationName);
-  g_pre_read_options.pre_read_chrome_child_in_browser =
-      ReadBool(key, kPreReadChromeChildInBrowser);
 }
 
 PreReadOptions GetPreReadOptions() {
diff --git a/components/startup_metric_utils/common/pre_read_field_trial_utils_win.h b/components/startup_metric_utils/common/pre_read_field_trial_utils_win.h
index f9e41a5..9bce57b 100644
--- a/components/startup_metric_utils/common/pre_read_field_trial_utils_win.h
+++ b/components/startup_metric_utils/common/pre_read_field_trial_utils_win.h
@@ -22,20 +22,16 @@ using RegisterPreReadSyntheticFieldTrialCallback =
 // The options controlled by the PreRead field trial.
 struct PreReadOptions {
   // Pre-read DLLs explicitly.
-  bool pre_read : 1;
+  bool pre_read;
 
   // Pre-read DLLs with a high thread priority.
-  bool high_priority : 1;
+  bool high_priority;
 
   // Pre-read DLLs using the ::PrefetchVirtualMemory function, if available.
-  bool prefetch_virtual_memory : 1;
+  bool prefetch_virtual_memory;
 
   // Use a /prefetch argument when launching a process.
-  bool use_prefetch_argument : 1;
-
-  // Pre-read chrome_child.dll in the browser process and not in child
-  // processes.
-  bool pre_read_chrome_child_in_browser : 1;
+  bool use_prefetch_argument;
 };
 
 // Initializes DLL pre-reading options from the registry.