Fixed two bugs in HttpCache

1. 304 responses always send "Content-Type: text/html; charset=UTF-8"
header
I discovered that the HttpCache::handle method calls Response::prepare
after calling Response::isModified.  Response::isModified removes the
Content-Type header as it should, but Response::handle adds in the
default Content-Type header when none is set.  If the default
Content-Type is not the correct Content-Type, then the Content-Type in
the cache gets clobered.  I solved this problem by moving the
Response::isModified call after the Response::prepare call.  I updated
the testRespondsWith304WhenIfModifiedSinceMatchesLastModified and
testRespondsWith304WhenIfNoneMatchMatchesETag tests to verify that the
Content-Type header was not being sent for 304 responses.

2. Failure to invalidate cached entities referred to by the Location
header
I discovered that the Store::invalidate method was looking for Location
and Content-Location headers to invalidate, but it was looking in the
request headers instead of the response headers.  Because the
Store::invalidate method doesn't take a response, I decided it was
better to move this logic to the HttpCache::invalidate method instead.
I updated the testInvalidatesCachedResponsesOnPost test to verify that
Location headers are getting invalidated correctly.

src/Symfony/Component/HttpKernel/HttpCache/HttpCache.php

@@ -193,8 +193,6 @@ class HttpCache implements HttpKernelInterface, TerminableInterface
             $response = $this->lookup($request, $catch);
         }
 
-        $response->isNotModified($request);
-
         $this->restoreResponseBody($request, $response);
 
         $response->setDate(new \DateTime(null, new \DateTimeZone('UTC')));
@@ -213,6 +211,8 @@ class HttpCache implements HttpKernelInterface, TerminableInterface
 
         $response->prepare($request);
 
+        $response->isNotModified($request);
+
         return $response;
     }
 
@@ -262,6 +262,15 @@ class HttpCache implements HttpKernelInterface, TerminableInterface
             try {
                 $this->store->invalidate($request, $catch);
 
+                // As per the RFC, invalidate Location and Content-Location URLs if present
+                foreach (array('Location', 'Content-Location') as $header) {
+                    if ($uri = $response->headers->get($header)) {
+                        $subRequest = $request::create($uri, 'get', array(), array(), array(), $request->server->all());
+
+                        $this->store->invalidate($subRequest);
+                    }
+                }
+
                 $this->record($request, 'invalidate');
             } catch (\Exception $e) {
                 $this->record($request, 'invalidate-failed');

src/Symfony/Component/HttpKernel/HttpCache/Store.php

@@ -231,15 +231,6 @@ class Store implements StoreInterface
                 throw new \RuntimeException('Unable to store the metadata.');
             }
         }
-
-        // As per the RFC, invalidate Location and Content-Location URLs if present
-        foreach (array('Location', 'Content-Location') as $header) {
-            if ($uri = $request->headers->get($header)) {
-                $subRequest = $request::create($uri, 'get', array(), array(), array(), $request->server->all());
-
-                $this->invalidate($subRequest);
-            }
-        }
     }
 
     /**

src/Symfony/Component/HttpKernel/Tests/HttpCache/HttpCacheTest.php

@@ -145,7 +145,7 @@ class HttpCacheTest extends HttpCacheTestCase
 
         $this->assertHttpKernelIsCalled();
         $this->assertEquals(304, $this->response->getStatusCode());
-        $this->assertEquals('text/html; charset=UTF-8', $this->response->headers->get('Content-Type'));
+        $this->assertEquals('', $this->response->headers->get('Content-Type'));
         $this->assertEmpty($this->response->getContent());
         $this->assertTraceContains('miss');
         $this->assertTraceContains('store');
@@ -158,7 +158,7 @@ class HttpCacheTest extends HttpCacheTestCase
 
         $this->assertHttpKernelIsCalled();
         $this->assertEquals(304, $this->response->getStatusCode());
-        $this->assertEquals('text/html; charset=UTF-8', $this->response->headers->get('Content-Type'));
+        $this->assertEquals('', $this->response->headers->get('Content-Type'));
         $this->assertTrue($this->response->headers->has('ETag'));
         $this->assertEmpty($this->response->getContent());
         $this->assertTraceContains('miss');
@@ -845,7 +845,7 @@ class HttpCacheTest extends HttpCacheTestCase
         $this->assertTraceContains('fresh');
 
         // now POST to same URL
-        $this->request('POST', '/');
+        $this->request('POST', '/helloworld');
         $this->assertHttpKernelIsCalled();
         $this->assertEquals('/', $this->response->headers->get('Location'));
         $this->assertTraceContains('invalidate');