Provide better diffs for object graphs that include objectContaining

Turns this output:
    Expected $[0].foo = Object({ a: 4, b: 5 }) to equal <jasmine.objectContaining(Object({ a: 1, c: 3 }))>.

into this:
    Expected $[0].foo.a = 4 to equal 1.
    Expected $[0].foo.c = undefined to equal 3.

And turns this output:
    Expected spy jasmineDone to have been called with:
       [ ... snipped very long expected call ]
    but actual calls were:
       [ ... snipped very long actual call ]

    Call 0:
      Expected $[0] = Object({ overallStatus: 'failed', totalTime: 1, incompleteReason: undefined, order: Order({ random: true, seed: '88732', sort: Function }), failedExpectations: [ Object({ matcherName: 'toBeResolved', passed: false, message: 'Suite "a suite" ran a "toBeResolved" expectation after it finished.
      Did you forget to return or await the result of expectAsync?', error: undefined, errorForStack: Error, actual: [object Promise], expected: [  ], globalErrorType: 'lateExpeztation' }) ], deprecationWarnings: [  ] }) to equal <jasmine.objectContaining(Object({ failedExpectations: [ <jasmine.objectContaining(Object({ passed: false, globalErrorType: 'lateExpectation', message: 'Suite "a suite" ran a "toBeResolved" expectation after it finished.
      Did you forget to return or await the result of expectAsync?', matcherName: 'toBeResolved' }))> ] }))>.

into this:
    Expected spy jasmineDone to have been called with:
       [ ... snipped very long expected call ]
    but actual calls were:
       [ ... snipped very long actual call ]

    Call 0:
      Expected $[0].failedExpectations[0].globalErrorType = 'lateExpeztation' to equal 'lateExpectation'.

src/core/asymmetric_equality/ObjectContaining.js

@@ -41,6 +41,27 @@ getJasmineRequireObj().ObjectContaining = function(j$) {
     return true;
   };
 
+  ObjectContaining.prototype.valuesForDiff_ = function(other) {
+    if (!j$.isObject_(other)) {
+      return {
+        self: this.jasmineToString(),
+        other: other
+      };
+    }
+
+    var filteredOther = {};
+    Object.keys(this.sample).forEach(function (k) {
+      // eq short-circuits comparison of objects that have different key sets,
+      // so include all keys even if undefined.
+      filteredOther[k] = other[k];
+    });
+
+    return {
+      self: this.sample,
+      other: filteredOther
+    };
+  };
+
   ObjectContaining.prototype.jasmineToString = function() {
     return '<jasmine.objectContaining(' + j$.pp(this.sample) + ')>';
   };

src/core/matchers/matchersUtil.js

@@ -55,7 +55,16 @@ getJasmineRequireObj().matchersUtil = function(j$) {
     return obj && j$.isA_('Function', obj.asymmetricMatch);
   }
 
-  function asymmetricMatch(a, b, customTesters, diffBuilder) {
+  function asymmetricDiff(a, b, aStack, bStack, customTesters, diffBuilder) {
+    if (j$.isFunction_(b.valuesForDiff_)) {
+      var values = b.valuesForDiff_(a);
+      eq(values.other, values.self, aStack, bStack, customTesters, diffBuilder);
+    } else {
+      diffBuilder.record(a, b);
+    }
+  }
+
+  function asymmetricMatch(a, b, aStack, bStack, customTesters, diffBuilder) {
     var asymmetricA = isAsymmetric(a),
         asymmetricB = isAsymmetric(b),
         result;
@@ -67,6 +76,8 @@ getJasmineRequireObj().matchersUtil = function(j$) {
     if (asymmetricA) {
       result = a.asymmetricMatch(b, customTesters);
       if (!result) {
+        // TODO: Do we want to build an asymmetric diff when the actual was an
+        // asymmeteric equality tester? Might be confusing.
         diffBuilder.record(a, b);
       }
       return result;
@@ -75,7 +86,7 @@ getJasmineRequireObj().matchersUtil = function(j$) {
     if (asymmetricB) {
       result = b.asymmetricMatch(a, customTesters);
       if (!result) {
-        diffBuilder.record(a, b);
+        asymmetricDiff(a, b, aStack, bStack, customTesters, diffBuilder);
       }
       return result;
     }
@@ -93,7 +104,7 @@ getJasmineRequireObj().matchersUtil = function(j$) {
   function eq(a, b, aStack, bStack, customTesters, diffBuilder) {
     var result = true, i;
 
-    var asymmetricResult = asymmetricMatch(a, b, customTesters, diffBuilder);
+    var asymmetricResult = asymmetricMatch(a, b, aStack, bStack, customTesters, diffBuilder);
     if (!j$.util.isUndefined(asymmetricResult)) {
       return asymmetricResult;
     }