Roll mojo (flutter#2881)

* Update to mojo ba13534f2b2af27a1d73e176f7406dbab25f8e14

* Fix build for updated mojo

* Fix android build. Undo some of the mojo roll.

* Fix iOS build.

DEPS

@@ -20,7 +20,7 @@
 vars = {
   'chromium_git': 'https://chromium.googlesource.com',
   'fuchsia_git': 'https://fuchsia.googlesource.com',
-  'mojo_sdk_revision': 'b200aa62c93647a0421b9239804ef5ce1509ab20',
+  'mojo_sdk_revision': '6b5fb1227c742f5ecc077486ebc029f2711c61fa',
   'base_revision': '672b04e54b937ec899429a6bd5409c5a6300d151',
   'skia_revision': 'd1bdd1fcbd308afb9903f39d231742f5c951cf07',
 
@@ -286,4 +286,29 @@ hooks = [
         'src/tools',
     ],
   },
+  # Pull the mojom generator binaries using checked-in hashes.
+  {
+    'name': 'mojom_generators',
+    'pattern': '',
+    'action': [ 'download_from_google_storage.py',
+                '--no_resume',
+                '--quiet',
+                '--platform=linux*',
+                '--no_auth',
+                '--bucket', 'mojo/mojom_parser/linux64/generators',
+                '-d', 'src/mojo/public/tools/bindings/mojom_tool/bin/linux64/generators',
+    ],
+  },
+  {
+    'name': 'mojom_generators',
+    'pattern': '',
+    'action': [ 'download_from_google_storage.py',
+                '--no_resume',
+                '--quiet',
+                '--platform=darwin',
+                '--no_auth',
+                '--bucket', 'mojo/mojom_parser/mac64/generators',
+                '-d', 'src/mojo/public/tools/bindings/mojom_tool/bin/mac64/generators',
+    ],
+  },
 ]

mojo/VERSION

@@ -1 +1 @@
-fd8d18dbf7a4f9ed8a607648cca6d2c595b1c580
+ba13534f2b2af27a1d73e176f7406dbab25f8e14

mojo/application/BUILD.gn

@@ -29,6 +29,7 @@ source_set("content_handler") {
     "//base",
     "//mojo/environment:chromium",
     "//mojo/message_pump",
+    "//mojo/public/cpp/bindings",
     "//mojo/public/interfaces/application",
     "//mojo/services/content_handler/interfaces",
     "//mojo/services/network/interfaces",

mojo/common/BUILD.gn

@@ -6,37 +6,22 @@ import("//mojo/public/mojo_application.gni")
 import("//mojo/public/tools/bindings/mojom.gni")
 import("//testing/test.gni")
 
-source_set("common") {
-  sources = [
-    "binding_set.h",
-    "interface_ptr_set.h",
-    "strong_binding_set.h",
-  ]
-
-  deps = [
-    "//base",
-    "//mojo/public/cpp/bindings",
-  ]
+# TODO(vtl): Remove this when tonic stops depending on a :common target.
+group("common") {
 }
 
+# TODO(vtl): callback_binding_unittest.cc is orphaned. This target (and
+# :mojo_common_apptests) should be moved somewhere else, but where?
 source_set("tests") {
   testonly = true
 
   sources = [
-    "binding_set_unittest.cc",
     "callback_binding_unittest.cc",
-    "interface_ptr_set_unittest.cc",
-    "strong_binding_set_unittest.cc",
   ]
 
   deps = [
-    ":common",
-    ":test_interfaces",
     "//base",
-    "//mojo/message_pump",
     "//mojo/public/cpp/bindings",
-    "//mojo/public/cpp/bindings:callback",
-    "//mojo/public/cpp/system",
     "//testing/gtest",
   ]
 }
@@ -51,13 +36,7 @@ mojo_native_application("mojo_common_apptests") {
   ]
 }
 
-mojom("test_interfaces") {
-  testonly = true
-  sources = [
-    "test_interfaces.mojom",
-  ]
-}
-
+# TODO(vtl): This should probably be moved into its own directory.
 source_set("tracing_impl") {
   sources = [
     "trace_provider_impl.cc",