Pass context to the constructor

This should reenable reading this.context from getInitialState.

Added a bunch of tests for this too.

src/classic/class/ReactClass.js

@@ -805,7 +805,7 @@ var ReactClass = {
    * @public
    */
   createClass: function(spec) {
-    var Constructor = function(props) {
+    var Constructor = function(props, context) {
       // This constructor is overridden by mocks. The argument is used
       // by mocks to assert on what gets mounted.
 
@@ -815,6 +815,7 @@ var ReactClass = {
       }
 
       this.props = props;
+      this.context = context;
       this.state = null;
 
       // ReactClasses doesn't have constructors. Instead, they use the

src/classic/class/__tests__/ReactClass-test.js

@@ -278,6 +278,36 @@ describe('ReactClass-spec', function() {
     expect(instance.state.occupation).toEqual('clown');
   });
 
+  it('renders based on context getInitialState', function() {
+    var Foo = React.createClass({
+      contextTypes: {
+        className: React.PropTypes.string
+      },
+      getInitialState() {
+        return { className: this.context.className };
+      },
+      render() {
+        return <span className={this.state.className} />;
+      }
+    });
+
+    var Outer = React.createClass({
+      childContextTypes: {
+        className: React.PropTypes.string
+      },
+      getChildContext() {
+        return { className: 'foo' };
+      },
+      render() {
+        return <Foo />;
+      }
+    });
+
+    var container = document.createElement('div');
+    React.render(<Outer />, container);
+    expect(container.firstChild.className).toBe('foo');
+  });
+
   it('should throw with non-object getInitialState() return values', function() {
     [['an array'], 'a string', 1234].forEach(function(state) {
       var Component = React.createClass({

src/core/ReactCompositeComponent.js

@@ -169,7 +169,7 @@ var ReactCompositeComponentMixin = assign({},
     );
 
     // Initialize the public class
-    var inst = new Component(publicProps);
+    var inst = new Component(publicProps, publicContext);
     // These should be set up in the constructor, but as a convenience for
     // simpler class abstractions, we set them up after the fact.
     inst.props = publicProps;

src/modern/class/ReactComponentBase.js

@@ -19,8 +19,9 @@ var warning = require('warning');
 /**
  * Base class helpers for the updating state of a component.
  */
-function ReactComponentBase(props) {
+function ReactComponentBase(props, context) {
   this.props = props;
+  this.context = context;
 }
 
 /**

src/modern/class/__tests__/ReactES6Class-test.js

@@ -98,6 +98,37 @@ describe('ReactES6Class', function() {
     test(<Foo />, 'SPAN', 'bar');
   });
 
+  it('renders based on context in the constructor', function() {
+    class Foo extends React.Component {
+      constructor(props, context) {
+        super(props, context);
+        this.state = { tag: context.tag, className: this.context.className };
+      }
+      render() {
+        var Tag = this.state.tag;
+        return <Tag className={this.state.className} />;
+      }
+    }
+    Foo.contextTypes = {
+      tag: React.PropTypes.string,
+      className: React.PropTypes.string
+    };
+
+    class Outer extends React.Component {
+      getChildContext() {
+        return { tag: 'span', className: 'foo' };
+      }
+      render() {
+        return <Foo />;
+      }
+    }
+    Outer.childContextTypes = {
+      tag: React.PropTypes.string,
+      className: React.PropTypes.string
+    };
+    test(<Outer />, 'SPAN', 'foo');
+  });
+
   it('renders only once when setting state in componentWillMount', function() {
     var renderCount = 0;
     class Foo extends React.Component {