Minor cleanup for ThemeOptionPreviewer

Test: Manually
Bug: 146475648
Change-Id: I54e196a3c28c46174901571d8347e8ff83765810
diff --git a/src/com/android/customization/picker/theme/ThemeOptionPreviewer.java b/src/com/android/customization/picker/theme/ThemeOptionPreviewer.java
index d9b7f4d..3f4381f 100644
--- a/src/com/android/customization/picker/theme/ThemeOptionPreviewer.java
+++ b/src/com/android/customization/picker/theme/ThemeOptionPreviewer.java
@@ -128,8 +128,8 @@
             public void onLayoutChange(View view, int left, int top, int right, int bottom,
                                        int oldLeft, int oldTop, int oldRight, int oldBottom) {
                 // Calculate the full preview card height and width.
-                int fullPreviewCardHeight = getFullPreviewCardHeight();
-                int fullPreviewCardWidth = (int) (getFullPreviewCardHeight() / screenAspectRatio);
+                final int fullPreviewCardHeight = getFullPreviewCardHeight();
+                final int fullPreviewCardWidth = (int) (fullPreviewCardHeight / screenAspectRatio);
 
                 // Relayout the content view to match full preview card size.
                 mContentView.measure(
@@ -139,8 +139,7 @@
 
                 // Scale the content view from full preview size to the container size. For full
                 // preview, the scale value is 1.
-                float scale =
-                        (float) previewContainer.getMeasuredHeight() / getFullPreviewCardHeight();
+                float scale = (float) previewContainer.getMeasuredHeight() / fullPreviewCardHeight;
                 mContentView.setScaleX(scale);
                 mContentView.setScaleY(scale);
                 // The pivot point is centered by default, set to (0, 0).