Default keyguard scrim should be 45% transparent

Wallpapers were barely visible on lock screen because value was set to
70%. The unlocked scrim (on the notification shade) was kept at 70% to
improve readability.

Also fixed a bug where scrim opacity wouldn't be overridden via overlay.

Bug: 63868547
Test: visual
Test: atest ScrimControllerTest
Change-Id: I17f277c917dc55604762420c0027b552993f1916
diff --git a/packages/SystemUI/src/com/android/systemui/statusbar/phone/ScrimController.java b/packages/SystemUI/src/com/android/systemui/statusbar/phone/ScrimController.java
index d6b45d6..ae93d98 100644
--- a/packages/SystemUI/src/com/android/systemui/statusbar/phone/ScrimController.java
+++ b/packages/SystemUI/src/com/android/systemui/statusbar/phone/ScrimController.java
@@ -92,7 +92,7 @@
     /**
      * Default alpha value for most scrims.
      */
-    public static final float GRADIENT_SCRIM_ALPHA = 0.70f;
+    public static final float GRADIENT_SCRIM_ALPHA = 0.45f;
     /**
      * A scrim varies its opacity based on a busyness factor, for example
      * how many notifications are currently visible.
diff --git a/packages/SystemUI/src/com/android/systemui/statusbar/phone/ScrimState.java b/packages/SystemUI/src/com/android/systemui/statusbar/phone/ScrimState.java
index bbdaa99..1c5df58 100644
--- a/packages/SystemUI/src/com/android/systemui/statusbar/phone/ScrimState.java
+++ b/packages/SystemUI/src/com/android/systemui/statusbar/phone/ScrimState.java
@@ -60,7 +60,7 @@
         @Override
         public float getBehindAlpha(float busynessFactor) {
             return MathUtils.map(0 /* start */, 1 /* stop */,
-                   ScrimController.GRADIENT_SCRIM_ALPHA, ScrimController.GRADIENT_SCRIM_ALPHA_BUSY,
+                   mScrimBehindAlphaKeyguard, ScrimController.GRADIENT_SCRIM_ALPHA_BUSY,
                    busynessFactor);
         }
     },