Moving gRPC support interfaces out of cronet and into a new component.

components/grpc_support/test/BUILD.gn

+source_set("unit_tests") {
+  testonly = true
+  sources = [
+    "get_stream_engine.cc",
+  ]
+
+  deps = [
+    ":quic_test_server",
+    "//base",
+    "//components/grpc_support",
+    "//components/grpc_support:bidirectional_stream_unittest",
+    "//net",
+    "//net:test_support",
+  ]
+}
+
+source_set("quic_test_server") {
+  testonly = true
+  sources = [
+    "quic_test_server.cc",
+    "quic_test_server.h",
+  ]
+
+  deps = [
+    "//base",
+    "//net",
+    "//net:simple_quic_tools",
+    "//net:test_support",
+  ]
+}
+
+source_set("get_stream_engine_header") {
+  testonly = true
+  sources = [
+    "get_stream_engine.h",
+  ]
+
+  deps = [
+    "//base",
+    "//net",
+  ]
+}