Add missing .h files to .gn files that have a .cc file next to it in the gn file already.

third_party/WebKit/Source/platform/BUILD.gn

Index: third_party/WebKit/Source/platform/BUILD.gn
diff --git a/third_party/WebKit/Source/platform/BUILD.gn b/third_party/WebKit/Source/platform/BUILD.gn
index e3220b447066853b792ededfe618f6478856cfe5..331ae70bf2f145218c68710e30386be2f4f1f734 100644
--- a/third_party/WebKit/Source/platform/BUILD.gn
+++ b/third_party/WebKit/Source/platform/BUILD.gn
@@ -1092,12 +1092,15 @@ component("platform") {
     "mediastream/MediaStreamWebAudioSource.cpp",
     "mediastream/MediaStreamWebAudioSource.h",
     "mhtml/ArchiveResource.cpp",
+    "mhtml/ArchiveResource.h",
     "mhtml/MHTMLArchive.cpp",
     "mhtml/MHTMLArchive.h",
     "mhtml/MHTMLParser.cpp",
     "mhtml/MHTMLParser.h",
     "mojo/BluetoothStructTraits.cpp",
+    "mojo/BluetoothStructTraits.h",
     "mojo/CommonCustomTypesStructTraits.cpp",
+    "mojo/CommonCustomTypesStructTraits.h",
     "mojo/MojoHelper.h",
     "network/ContentSecurityPolicyParsers.cpp",
     "network/ContentSecurityPolicyParsers.h",
@@ -1554,7 +1557,9 @@ static_library("test_support") {
     "network/mime/MockMimeRegistry.h",
     "scheduler/base/task_queue_manager_delegate_for_test.cc",
     "scheduler/base/test_time_source.cc",
+    "scheduler/base/test_time_source.h",
     "scheduler/child/scheduler_tqm_delegate_for_test.cc",
+    "scheduler/child/scheduler_tqm_delegate_for_test.h",
     "scheduler/test/fake_renderer_scheduler.cc",
     "scheduler/test/fake_web_task_runner.cc",
     "scheduler/test/fake_web_task_runner.h",
@@ -1690,6 +1695,7 @@ test("blink_platform_unittests") {
     "geometry/DoubleRectTest.cpp",
     "geometry/FloatBoxTest.cpp",
     "geometry/FloatBoxTestHelpers.cpp",
+    "geometry/FloatBoxTestHelpers.h",
     "geometry/FloatPointTest.cpp",
     "geometry/FloatPolygonTest.cpp",
     "geometry/FloatQuadTest.cpp",
@@ -1697,6 +1703,7 @@ test("blink_platform_unittests") {
     "geometry/FloatRoundedRectTest.cpp",
     "geometry/FloatSizeTest.cpp",
     "geometry/GeometryTestHelpers.cpp",
+    "geometry/GeometryTestHelpers.h",
     "geometry/IntRectTest.cpp",
     "geometry/LayoutRectOutsetsTest.cpp",
     "geometry/LayoutRectTest.cpp",
@@ -1753,6 +1760,7 @@ test("blink_platform_unittests") {
     "scheduler/base/task_queue_manager_unittest.cc",
     "scheduler/base/task_queue_selector_unittest.cc",
     "scheduler/base/test_count_uses_time_source.cc",
+    "scheduler/base/test_count_uses_time_source.h",
     "scheduler/base/thread_load_tracker_unittest.cc",
     "scheduler/base/time_domain_unittest.cc",
     "scheduler/base/work_queue_sets_unittest.cc",