Add FilePath to base namespace.

net/disk_cache/mapped_file.h

Index: net/disk_cache/mapped_file.h
diff --git a/net/disk_cache/mapped_file.h b/net/disk_cache/mapped_file.h
index c5960d0c6ba1658bce26e31de20a8206ab1bc935..61909975422de6b57d92a74d7b7e4b53f503655b 100644
--- a/net/disk_cache/mapped_file.h
+++ b/net/disk_cache/mapped_file.h
@@ -12,7 +12,9 @@
 #include "net/disk_cache/file.h"
 #include "net/disk_cache/file_block.h"
 
+namespace base {
 class FilePath;
+}
 
 namespace disk_cache {
 
@@ -27,7 +29,7 @@ class NET_EXPORT_PRIVATE MappedFile : public File {
   // Performs object initialization. name is the file to use, and size is the
   // amount of data to memory map from the file. If size is 0, the whole file
   // will be mapped in memory.
-  void* Init(const FilePath& name, size_t size);
+  void* Init(const base::FilePath& name, size_t size);
 
   void* buffer() const {
     return buffer_;