[ios] UI Polish Omnibox: add animation to DSE favicon.

Current behaviour:
When focusing the Omnibox, the icon on the far left (G icon, Favicon,
e.g.) has no animation.

Intended behaviour:
The icon on the far left should have a short animation starting from an
opacity of 0 and a scale of 0 towards an opacity of 100 and a scale of 1.

Bug: none.
Change-Id: I06a90707db4e496fe1aef032e2ce110f392e3d81
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2339531Reviewed-by: Stepan Khapugin <stkhapugin@chromium.org>
Commit-Queue: Nazerke Kalidolda <nazerke@google.com>
Cr-Commit-Position: refs/heads/master@{#796931}

ios/chrome/browser/ui/omnibox/omnibox_container_view.h

@@ -37,6 +37,9 @@
 // Sets the alpha level of the leading image view.
 - (void)setLeadingImageAlpha:(CGFloat)alpha;
 
+// Sets the scale of the leading image view.
+- (void)setLeadingImageScale:(CGFloat)scaleValue;
+
 // Asks the container view to attch any layout guides to its views.
 - (void)attachLayoutGuides;
 

ios/chrome/browser/ui/omnibox/omnibox_container_view.mm

@@ -117,6 +117,10 @@ const CGFloat kTextFieldClearButtonTrailingOffset = 4;
   self.leadingImageView.alpha = alpha;
 }
 
+- (void)setLeadingImageScale:(CGFloat)scaleValue {
+  self.leadingImageView.transform =
+      CGAffineTransformMakeScale(scaleValue, scaleValue);
+}
 #pragma mark - private
 
 - (void)setupLeadingImageViewWithTint:(UIColor*)iconTint {

ios/chrome/browser/ui/omnibox/omnibox_view_controller.mm

@@ -364,7 +364,19 @@ const CGFloat kClearButtonSize = 28.0f;
 #pragma mark - EditViewAnimatee
 
 - (void)setLeadingIconFaded:(BOOL)faded {
-  [self.view setLeadingImageAlpha:faded ? 0 : 1];
+  CATransition* transition = [CATransition animation];
+  transition.duration = 0.3;
+  transition.timingFunction = [CAMediaTimingFunction
+      functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
+  transition.type = kCATransitionFade;
+  [self.view.layer addAnimation:transition forKey:nil];
+  if (faded) {
+    [self.view setLeadingImageAlpha:0];
+    [self.view setLeadingImageScale:0];
+  } else {
+    [self.view setLeadingImageAlpha:1];
+    [self.view setLeadingImageScale:1];
+  }
 }
 
 - (void)setClearButtonFaded:(BOOL)faded {