Add missing mock headers to api.

R=mbonadei@webrtc.org

Bug: webrtc:7618
Change-Id: Ia622a7623b2fa05ec14b52d5d31d158d1bd0ef6d
Reviewed-on: https://webrtc-review.googlesource.com/34644
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Commit-Queue: Patrik Höglund <phoglund@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#21364}

api/BUILD.gn

@@ -304,6 +304,20 @@ if (rtc_include_tests) {
     ]
   }
 
+  rtc_source_set("mock_rtp") {
+    testonly = true
+    sources = [
+      "test/mock_rtpreceiver.h",
+      "test/mock_rtpsender.h",
+    ]
+
+    deps = [
+      ":libjingle_peerconnection_api",
+      "../test:test_support",
+      "//testing/gmock",
+    ]
+  }
+
   rtc_source_set("mock_video_codec_factory") {
     testonly = true
     sources = [

pc/BUILD.gn

@@ -442,6 +442,7 @@ if (rtc_include_tests) {
     deps = [
       ":peerconnection",
       ":rtc_pc_base",
+      "../api:mock_rtp",
       "../rtc_base:checks",
       "../rtc_base:stringutils",
     ]