explicitly delete our c++ window on quit

BUG=skia:
TBR=
NOTRY=True

Review URL: https://codereview.chromium.org/633923002

src/views/mac/SampleAppDelegate.mm

@@ -18,6 +18,7 @@
 }
 
 - (NSApplicationTerminateReply)applicationShouldTerminate:(NSApplication *)sender {
+    [fView freeNativeWind];
     application_term();
     return NSTerminateNow;
 }

src/views/mac/SkNSView.h

@@ -49,4 +49,7 @@ class SkEvent;
 - (bool)attach:(SkOSWindow::SkBackEndTypes)attachType withMSAASampleCount:(int) sampleCount andGetInfo:(SkOSWindow::AttachmentInfo*) info;
 - (void)detach;
 - (void)present;
+
+- (void)freeNativeWind;
+
 @end

src/views/mac/SkNSView.mm

@@ -118,12 +118,17 @@ SK_COMPILE_ASSERT(SK_SUPPORT_GPU, not_implemented_for_non_gpu_build);
 }
 
 - (void)dealloc {
-    delete fWind;
+    [self freeNativeWind];
     self.fGLContext = nil;
     self.fTitle = nil;
     [super dealloc];
 }
 
+- (void)freeNativeWind {
+    delete fWind;
+    fWind = nil;
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 
 - (void)drawSkia {

src/views/mac/SkSampleNSView.mm

@@ -18,11 +18,6 @@
     return self;
 }
 
-- (void)dealloc {
-    delete fWind;
-    [super dealloc];
-}
-
 - (void)swipeWithEvent:(NSEvent *)event {
     CGFloat x = [event deltaX];
     if (x < 0)