Mojo: Move platform handle/channel stuff in system to embedder namespace.

mojo/system/platform_channel_pair.h

Index: mojo/system/platform_channel_pair.h
diff --git a/mojo/system/platform_channel_pair.h b/mojo/system/platform_channel_pair.h
index 3bea18ee25fe9f95972c2a3e43b26ad0bce1182f..41ca32f791ce4d2cf7bd606f66b194f1bd32f901 100644
--- a/mojo/system/platform_channel_pair.h
+++ b/mojo/system/platform_channel_pair.h
@@ -14,7 +14,7 @@
 class CommandLine;
 
 namespace mojo {
-namespace system {
+namespace embedder {
 
 // This is used to create a pair of |PlatformHandle|s that are connected by a
 // suitable (platform-specific) bidirectional "pipe" (e.g., socket on POSIX,
@@ -67,7 +67,7 @@ class MOJO_SYSTEM_IMPL_EXPORT PlatformChannelPair {
   DISALLOW_COPY_AND_ASSIGN(PlatformChannelPair);
 };
 
-}  // namespace system
+}  // namespace embedder
 }  // namespace mojo
 
 #endif  // MOJO_SYSTEM_PLATFORM_CHANNEL_PAIR_H_