minui: Add support for multiple connectors

Add support for multiple connectors.

Bug: 194732653
Test: charging animation can be displayed on different connectors
Change-Id: If9b9eac25ce6e4c582aeb7c52e94ca266f623438
diff --git a/minui/graphics.h b/minui/graphics.h
index 3c45a40..5408c93 100644
--- a/minui/graphics.h
+++ b/minui/graphics.h
@@ -21,6 +21,12 @@
 
 class MinuiBackend {
  public:
+  enum DrmConnector {
+    DRM_MAIN = 0,
+    DRM_SEC,
+    DRM_MAX,
+  };
+
   // Initializes the backend and returns a GRSurface* to draw into.
   virtual GRSurface* Init() = 0;
 
@@ -28,9 +34,12 @@
   // be displayed, and returns a new drawing surface.
   virtual GRSurface* Flip() = 0;
 
-  // Blank (or unblank) the screen.
+  // Blank (or unblank) the default screen.
   virtual void Blank(bool) = 0;
 
+  // Blank (or unblank) the specific screen.
+  virtual void Blank(bool blank, DrmConnector index) = 0;
+
   // Device cleanup when drawing is done.
   virtual ~MinuiBackend() {};
 };