[ios clean] Remove stop on Browser coordinator dealloc

The previous code caused that dismissing the ToolMenu would dismiss the whole Tab
(Toolbar+content view) and left the App in a corrupted state. (The coordinators were
not stopped but their VC was dismissed).

This is a temporary fix. Marq will submit a more robust solution to this problem later on.

BUG=

Review-Url: https://codereview.chromium.org/2667873002
Cr-Commit-Position: refs/heads/master@{#448040}

ios/clean/chrome/browser/browser_coordinator.h

@@ -39,7 +39,7 @@ class ChromeBrowserState;
 // it.
 - (void)start;
 
-// Stops the user interaction managed by the receiver. Called on dealloc.
+// Stops the user interaction managed by the receiver.
 - (void)stop;
 
 @end

ios/clean/chrome/browser/browser_coordinator.mm

@@ -40,10 +40,6 @@
   return self;
 }
 
-- (void)dealloc {
-  [self stop];
-}
-
 #pragma mark - Public API
 
 - (void)start {

ios/clean/chrome/browser/browser_coordinator_unittest.mm

@@ -50,7 +50,7 @@
 
 namespace {
 
-TEST(BrowserCoordinatorTest, TestStopOnDealloc) {
+TEST(BrowserCoordinatorTest, TestDontStopOnDealloc) {
   __block BOOL called = NO;
 
   {
@@ -60,7 +60,7 @@ TEST(BrowserCoordinatorTest, TestStopOnDealloc) {
     };
   }
 
-  EXPECT_TRUE(called);
+  EXPECT_FALSE(called);
 }
 
 TEST(BrowserCoordinatorTest, TestChildren) {