reland 31875. Revert was:

------
Revert 31875 to see whether it fixes reliability bot.

BUG=25677
TEST=None
------

TBR=huanr
Review URL: http://codereview.chromium.org/397017

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@32112 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 27 insertions, 0 deletions

diff --git a/base/file_util.cc b/base/file_util.cc
index 4cde773..8d1b517 100644
--- a/base/file_util.cc
+++ b/base/file_util.cc
@@ -267,6 +267,20 @@ MemoryMappedFile::~MemoryMappedFile() {
   CloseHandles();
 }
 
+bool MemoryMappedFile::Initialize(base::PlatformFile file) {
+  if (IsValid())
+    return false;
+
+  file_ = file;
+
+  if (!MapFileToMemoryInternal()) {
+    CloseHandles();
+    return false;
+  }
+
+  return true;
+}
+
 bool MemoryMappedFile::Initialize(const FilePath& file_name) {
   if (IsValid())
     return false;
@@ -279,6 +293,19 @@ bool MemoryMappedFile::Initialize(const FilePath& file_name) {
   return true;
 }
 
+bool MemoryMappedFile::MapFileToMemory(const FilePath& file_name) {
+  file_ = base::CreatePlatformFile(file_name,
+      base::PLATFORM_FILE_OPEN | base::PLATFORM_FILE_READ,
+      NULL);
+
+  if (file_ == base::kInvalidPlatformFileValue) {
+    LOG(ERROR) << "Couldn't open " << file_name.value();
+    return false;
+  }
+
+  return MapFileToMemoryInternal();
+}
+
 bool MemoryMappedFile::IsValid() {
   return data_ != NULL;
 }