Add dawn_wire entrypoints to inject texture in the wire

This allows reserving a texture ID in the client and injecting textures
in the wire, so that the WebGPU control channel can create WebGPU
textures backed by SharedImages in Chromium.

BUG=941543

Change-Id: I1efcfe3dce024bb2d3592f22225407a97b641c1f
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/5820
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Austin Eng <enga@chromium.org>

src/tests/unittests/wire/WireTest.cpp

@@ -74,6 +74,18 @@ void WireTest::FlushServer() {
     ASSERT_TRUE(mS2cBuf->Flush());
 }
 
+dawn_wire::WireServer* WireTest::GetWireServer() {
+    return mWireServer.get();
+}
+
+dawn_wire::WireClient* WireTest::GetWireClient() {
+    return mWireClient.get();
+}
+
+void WireTest::DeleteServer() {
+    mWireServer = nullptr;
+}
+
 void WireTest::SetupIgnoredCallExpectations() {
     if (mIgnoreSetCallbackCalls) {
         EXPECT_CALL(api, OnBuilderSetErrorCallback(_, _, _, _)).Times(AnyNumber());