[fuchsia] Convert fidl_interface_request_mojom_traits.h and its users to handle<platform>

Bug: 778317
Change-Id: I9d9ab96a40d9ba664428d7e514ba3fcc314a9a0f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2065317
Commit-Queue: Robert Sesek <rsesek@chromium.org>
Reviewed-by: Wez <wez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#743136}

fuchsia/mojom/example.mojom

@@ -7,5 +7,5 @@ module fuchsia.test.mojom;
 // Mojo struct of fidl::InterfaceRequest<TestInterface>. |request| is a
 // channel handle.
 struct TestInterfaceRequest {
-  handle request;
+  handle<platform> request;
 };

fuchsia/mojom/fidl_interface_request_mojom_traits.h

@@ -8,7 +8,6 @@
 #include <lib/fidl/cpp/interface_request.h>
 
 #include "mojo/public/cpp/platform/platform_handle.h"
-#include "mojo/public/cpp/system/platform_handle.h"
 
 namespace mojo {
 
@@ -17,19 +16,13 @@ namespace mojo {
 // this struct. Read test_request_interface_mojom_traits.h for an example.
 template <typename DataView, typename Interface>
 struct FidlInterfaceRequestStructTraits {
-  static ScopedHandle request(fidl::InterfaceRequest<Interface>& request) {
+  static PlatformHandle request(fidl::InterfaceRequest<Interface>& request) {
     DCHECK(request.is_valid());
-    PlatformHandle handle(request.TakeChannel());
-    return WrapPlatformHandle(std::move(handle));
+    return PlatformHandle(request.TakeChannel());
   }
 
   static bool Read(DataView input, fidl::InterfaceRequest<Interface>* output) {
-    ScopedHandle input_request = input.TakeRequest();
-    if (!input_request.is_valid())
-      return false;
-
-    PlatformHandle handle =
-        mojo::UnwrapPlatformHandle(std::move(input_request));
+    PlatformHandle handle = input.TakeRequest();
     if (!handle.is_valid_handle())
       return false;
 

media/fuchsia/mojom/fuchsia_audio_consumer_provider.mojom

@@ -6,7 +6,7 @@ module media.mojom;
 
 // Mojo struct for fidl::InterfaceRequest<fuchsia::media::AudioConsumer>.
 struct AudioConsumerRequest {
-  handle request;
+  handle<platform> request;
 };
 
 // Interface used by FuchsiaAudioRenderer to create AudioConsumer.

media/fuchsia/mojom/fuchsia_cdm_provider.mojom

@@ -7,7 +7,7 @@ module media.mojom;
 // Mojo struct for
 // fidl::InterfaceRequest<fuchsia::media::drm::ContentDecryptionModule>.
 struct CdmRequest {
-  handle request;
+  handle<platform> request;
 };
 
 // Interface for asking privileged process to create connection to