Add Trace points to WallpaperColors

WallpaperColors processes Bitmaps which can be slow (and cause jank)
when called on the main thread. This adds trace points so we can debug
these calls as a source of jank.

Bug: 287209189

Test: ran a perfetto trace on device
Change-Id: If0cb5d3d6bf04c404fae2b1a6229cdb92946526b

core/java/android/app/WallpaperColors.java

@@ -28,6 +28,7 @@ import android.graphics.drawable.Drawable;
 import android.os.Parcel;
 import android.os.Parcelable;
 import android.os.SystemProperties;
+import android.os.Trace;
 import android.util.Log;
 import android.util.MathUtils;
 import android.util.Size;
@@ -144,6 +145,7 @@ public final class WallpaperColors implements Parcelable {
             throw new IllegalArgumentException("Drawable cannot be null");
         }
 
+        Trace.beginSection("WallpaperColors#fromDrawable");
         Rect initialBounds = drawable.copyBounds();
         int width = drawable.getIntrinsicWidth();
         int height = drawable.getIntrinsicHeight();
@@ -165,6 +167,7 @@ public final class WallpaperColors implements Parcelable {
         bitmap.recycle();
 
         drawable.setBounds(initialBounds);
+        Trace.endSection();
         return colors;
     }
 
@@ -195,7 +198,7 @@ public final class WallpaperColors implements Parcelable {
     public static WallpaperColors fromBitmap(@NonNull Bitmap bitmap,
             @FloatRange (from = 0f, to = 1f) float dimAmount) {
         Objects.requireNonNull(bitmap, "Bitmap can't be null");
-
+        Trace.beginSection("WallpaperColors#fromBitmap");
         final int bitmapArea = bitmap.getWidth() * bitmap.getHeight();
         boolean shouldRecycle = false;
         if (bitmapArea > MAX_WALLPAPER_EXTRACTION_AREA) {
@@ -247,6 +250,7 @@ public final class WallpaperColors implements Parcelable {
             bitmap.recycle();
         }
 
+        Trace.endSection();
         return new WallpaperColors(populationByColor, HINT_FROM_BITMAP | hints);
     }
 
@@ -462,7 +466,7 @@ public final class WallpaperColors implements Parcelable {
      * Gets the most visually representative color of the wallpaper.
      * "Visually representative" means easily noticeable in the image,
      * probably happening at high frequency.
-     *
+     *fromBitmap
      * @return A color.
      */
     public @NonNull Color getPrimaryColor() {
@@ -545,6 +549,7 @@ public final class WallpaperColors implements Parcelable {
             return 0;
         }
 
+        Trace.beginSection("WallpaperColors#calculateDarkHints");
         dimAmount = MathUtils.saturate(dimAmount);
         int[] pixels = new int[source.getWidth() * source.getHeight()];
         double totalLuminance = 0;
@@ -607,6 +612,7 @@ public final class WallpaperColors implements Parcelable {
                     " maxD: " + maxDarkPixels + " numPixels: " + pixels.length);
         }
 
+        Trace.endSection();
         return hints;
     }