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

mojo/public/dart/third_party/yaml/CHANGELOG.md

+## 2.1.3
+
+* Add a hint that a colon might be missing when a mapping value is found in the
+  wrong context.
+
+## 2.1.2
+
+* Fix a crashing bug when parsing block scalars.
+
+## 2.1.1
+
+* Properly scope `SourceSpan`s for scalar values surrounded by whitespace.
+
+## 2.1.0
+
+* Rewrite the parser for a 10x speed improvement.
+
+* Support anchors and aliases (`&foo` and `*foo`).
+
+* Support explicit tags (e.g. `!!str`). Note that user-defined tags are still
+  not fully supported.
+
+* `%YAML` and `%TAG` directives are now parsed, although again user-defined tags
+  are not fully supported.
+
+* `YamlScalar`, `YamlList`, and `YamlMap` now expose the styles in which they
+  were written (for example plain vs folded, block vs flow).
+
+* A `yamlWarningCallback` field is exposed. This field can be used to customize
+  how YAML warnings are displayed.
+
+## 2.0.1+1
+
+* Fix an import in a test.
+
+* Widen the version constraint on the `collection` package.
+
+## 2.0.1
+
+* Fix a few lingering references to the old `Span` class in documentation and
+  tests.
+
+## 2.0.0
+
+* Switch from `source_maps`' `Span` class to `source_span`'s `SourceSpan` class.
+
+* For consistency with `source_span` and `string_scanner`, all `sourceName`
+  parameters have been renamed to `sourceUrl`. They now accept Urls as well as
+  Strings.
+
+## 1.1.1
+
+* Fix broken type arguments that caused breakage on dart2js.
+
+* Fix an analyzer warning in `yaml_node_wrapper.dart`.
+
+## 1.1.0
+
+* Add new publicly-accessible constructors for `YamlNode` subclasses. These
+  constructors make it possible to use the same API to access non-YAML data as
+  YAML data.
+
+* Make `YamlException` inherit from source_map's [`SpanFormatException`][]. This
+  improves the error formatting and allows callers access to source range
+  information.
+
+[SpanFormatException]: (http://www.dartdocs.org/documentation/source_maps/0.9.2/index.html#source_maps/source_maps.SpanFormatException)
+
+## 1.0.0+1
+
+* Fix a variable name typo.
+
+## 1.0.0
+
+* **Backwards incompatibility**: The data structures returned by `loadYaml` and
+  `loadYamlStream` are now immutable.
+
+* **Backwards incompatibility**: The interface of the `YamlMap` class has
+  changed substantially in numerous ways. External users may no longer construct
+  their own instances.
+
+* Maps and lists returned by `loadYaml` and `loadYamlStream` now contain
+  information about their source locations.
+
+* A new `loadYamlNode` function returns the source location of top-level scalars
+  as well.
+
+## 0.10.0
+
+* Improve error messages when a file fails to parse.
+
+## 0.9.0+2
+
+* Ensure that maps are order-independent when used as map keys.
+
+## 0.9.0+1
+
+* The `YamlMap` class is deprecated. In a future version, maps returned by
+  `loadYaml` and `loadYamlStream` will be Dart `HashMap`s with a custom equality
+  operation.