Stop running pub get at gclient sync time and fix build bugs

.gitignore

Index: .gitignore
diff --git a/.gitignore b/.gitignore
index 9d30a0f1623560c04ab4acddbbcaf45fd9699eba..2b07bd730d1b72cbe6bdffe59807509bea08adbc 100644
--- a/.gitignore
+++ b/.gitignore
@@ -24,8 +24,7 @@ v8.log
 # directories pulled in via deps or hooks
 /build/linux/bin/eu-strip
 /buildtools/
-/dart/
-/dart-pub-cache/
+/mojo/public/third_party/dart/
 /native_client/
 /out/
 /out_*/
@@ -40,20 +39,9 @@ v8.log
 /third_party/brotli/src/
 /third_party/colorama/src/
 /third_party/dart-sdk/
-/third_party/dart-pkg/archive
-/third_party/dart-pkg/args
-/third_party/dart-pkg/box2d
-/third_party/dart-pkg/cassowary
-/third_party/dart-pkg/collection
-/third_party/dart-pkg/crypto
-/third_party/dart-pkg/newton
-/third_party/dart-pkg/path
-/third_party/dart-pkg/quiver
-/third_party/dart-pkg/source_span
-/third_party/dart-pkg/string_scanner
-/third_party/dart-pkg/vector_math
-/third_party/dart-pkg/vector_math
-/third_party/dart-pkg/yaml
+/mojo/public/third_party/dart-pkg/*
+!/mojo/public/third_party/dart-pkg/BUILD.gn
+!/mojo/public/third_party/dart-pkg/README.md
 /third_party/dejavu-fonts-ttf-2.34/ttf/*.ttf
 /third_party/freetype-android/src
 /third_party/go/