Minor tweaks to API documentation and code comments.

mojo/public/c/system/buffer.h

Index: mojo/public/c/system/buffer.h
diff --git a/mojo/public/c/system/buffer.h b/mojo/public/c/system/buffer.h
index 97bc340f04b1e378d5faaadf874cc1352651545b..45d2c2d761fb32d86a39a80c77b7b14584b35c11 100644
--- a/mojo/public/c/system/buffer.h
+++ b/mojo/public/c/system/buffer.h
@@ -169,9 +169,9 @@ MOJO_SYSTEM_EXPORT MojoResult MojoMapBuffer(MojoHandle buffer_handle,
                                             MojoMapBufferFlags flags);
 
 // Unmaps a buffer pointer that was mapped by |MojoMapBuffer()|. |buffer| must
-// have been the result of |MojoMapBuffer()| (not some pointer strictly inside
+// have been the result of |MojoMapBuffer()| (not some other pointer inside
 // the mapped memory), and the entire mapping will be removed (partial unmapping
-// is not supported). A mapping may only be unmapped exactly once.
+// is not supported). A mapping may only be unmapped once.
 //
 // Returns:
 //   |MOJO_RESULT_OK| on success.