Fix the case where the browser livelocks if we cannot open a file.

base/platform_file.h

Index: base/platform_file.h
diff --git a/base/platform_file.h b/base/platform_file.h
index 0dbf4e4aa7cdce1e623f023c0ba0e762049fa604..46ff0ccf73c0af7a7143c14ee3872ae3053a9623 100644
--- a/base/platform_file.h
+++ b/base/platform_file.h
@@ -6,6 +6,8 @@
 #define BASE_PLATFORM_FILE_H_
 
 #include "build/build_config.h"
+#include "base/basictypes.h"
+
 #if defined(OS_WIN)
 #include <windows.h>
 #endif
@@ -53,6 +55,10 @@ PlatformFile CreatePlatformFile(const std::wstring& name,
 // Closes a file handle
 bool ClosePlatformFile(PlatformFile file);
 
+// Get the length of an underlying file. Returns false on error. Otherwise
+// *size is set to the length of the file, in bytes.
+bool GetPlatformFileSize(PlatformFile file, uint64* size);
+
 }  // namespace base
 
 #endif  // BASE_PLATFORM_FILE_H_