Mojo C++ Bindings: Remove redundant AssociatedInterfaceRequest APIs

Adds an explicit constructor over a ScopedInterfaceEndpointHandle and
removes the Bind method. Also removes the now-useless
MakeAssocaiatedRequest template helper.

BUG=721507
[email protected]
[email protected]

Change-Id: I80f90460bcbb2b275e9609205d5d1c112edb0325
Reviewed-on: https://chromium-review.googlesource.com/505330
Reviewed-by: Ken Rockot <[email protected]>
Reviewed-by: Yuzhu Shen <[email protected]>
Commit-Queue: Ken Rockot <[email protected]>
Cr-Commit-Position: refs/heads/master@{#471886}
20 files changed