Implement SharedMemory::NewAnonymousReadOnly(contents).

base/memory/shared_memory.h

Index: base/memory/shared_memory.h
diff --git a/base/memory/shared_memory.h b/base/memory/shared_memory.h
index 23f6973374a0da00e1f1fb94cb99f8723ecae352..214afb7c0d71ea915977f9c00db18e0ba5854d5d 100644
--- a/base/memory/shared_memory.h
+++ b/base/memory/shared_memory.h
@@ -17,6 +17,7 @@
 
 #include "base/base_export.h"
 #include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"
 #include "base/process/process_handle.h"
 
 #if defined(OS_POSIX)
@@ -80,6 +81,11 @@ class BASE_EXPORT SharedMemory {
 
   // Create a new SharedMemory object from an existing, open
   // shared memory file.
+  //
+  // WARNING: This does not reduce the OS-level permissions on the handle; it
+  // only affects how the SharedMemory will be mmapped.  TODO(jln,jyasskin):
+  // remove this overload or DCHECK that read_only matches the permissions of
+  // the handle.
   SharedMemory(SharedMemoryHandle handle, bool read_only);
 
   // Create a new SharedMemory object from an existing, open
@@ -104,6 +110,11 @@ class BASE_EXPORT SharedMemory {
   // Returns the maximum number of handles that can be open at once per process.
   static size_t GetHandleLimit();
 
+  // Returns a new, read-only, unmapped SharedMemory with |contents| written
+  // into it.  Use this to send data to untrusted processes.  Returns NULL if
+  // creation fails.
+  static scoped_ptr<SharedMemory> NewAnonymousReadOnly(StringPiece contents);
+
   // Creates a shared memory object as described by the options struct.
   // Returns true on success and false on failure.
   bool Create(const SharedMemoryCreateOptions& options);