fix(di): capture original exception in InvalidBindingError

Fixes #1406

Closes #1459

modules/angular2/src/di/exceptions.js

@@ -140,13 +140,17 @@ export class CyclicDependencyError extends AbstractBindingError {
  * @exportedAs angular2/di_errors
  */
 export class InstantiationError extends AbstractBindingError {
+  cause;
+  causeKey;
   // TODO(tbosch): Can't do key:Key as this results in a circular dependency!
-  constructor(originalException, key) {
+  constructor(cause, key) {
     super(key, function (keys:List) {
       var first = stringify(ListWrapper.first(keys).token);
       return `Error during instantiation of ${first}!${constructResolvingPath(keys)}.` +
-        ` ORIGINAL ERROR: ${originalException}`;
+        ` ORIGINAL ERROR: ${cause}`;
     });
+    this.cause = cause;
+    this.causeKey = key;
   }
 }
 

modules/angular2/test/di/injector_spec.js

@@ -1,4 +1,4 @@
-import {isBlank} from 'angular2/src/facade/lang';
+import {isBlank, BaseException} from 'angular2/src/facade/lang';
 import {describe, ddescribe, it, iit, expect, beforeEach} from 'angular2/test_lib';
 import {Injector, Inject, InjectLazy, Optional, bind, ResolvedBinding} from 'angular2/di';
 
@@ -7,7 +7,7 @@ class Engine {
 
 class BrokenEngine {
   constructor() {
-    throw "Broken Engine";
+    throw new BaseException("Broken Engine");
   }
 }
 
@@ -251,6 +251,8 @@ export function main() {
         throw "Must throw";
       } catch (e) {
         expect(e.message).toContain("Error during instantiation of Engine! (Car -> Engine)");
+        expect(e.cause instanceof BaseException).toBeTruthy();
+        expect(e.causeKey.token).toEqual(Engine);
       }
     });