[Shadows] Add shadow vertex generation code and shaders [8/n]

Bug: 136561771
Test: go/wm-smoke

Change-Id: I13e627a707d6d7a10bbd0ea6cc26bcb5c5bc9ab8
diff --git a/libs/renderengine/gl/ProgramCache.h b/libs/renderengine/gl/ProgramCache.h
index 175c6e8..c8b6da7 100644
--- a/libs/renderengine/gl/ProgramCache.h
+++ b/libs/renderengine/gl/ProgramCache.h
@@ -112,6 +112,11 @@
             Y410_BT2020_MASK = 1 << Y410_BT2020_SHIFT,
             Y410_BT2020_OFF = 0 << Y410_BT2020_SHIFT,
             Y410_BT2020_ON = 1 << Y410_BT2020_SHIFT,
+
+            SHADOW_SHIFT = 13,
+            SHADOW_MASK = 1 << SHADOW_SHIFT,
+            SHADOW_OFF = 0 << SHADOW_SHIFT,
+            SHADOW_ON = 1 << SHADOW_SHIFT,
         };
 
         inline Key() : mKey(0) {}
@@ -130,6 +135,7 @@
         inline bool hasRoundedCorners() const {
             return (mKey & ROUNDED_CORNERS_MASK) == ROUNDED_CORNERS_ON;
         }
+        inline bool drawShadows() const { return (mKey & SHADOW_MASK) == SHADOW_ON; }
         inline bool hasInputTransformMatrix() const {
             return (mKey & INPUT_TRANSFORM_MATRIX_MASK) == INPUT_TRANSFORM_MATRIX_ON;
         }