SurfaceControl: Add setDropInputMode api

Introduces an API to drop input events on this SurfaceControl. This
policy will be inherited by its children. The caller must hold the
ACCESS_SURFACE_FLINGER permission.

Options include:
ALL: SurfaceControl and its children will not receive any
input regardless of whether it has a valid input channel.

These policies are used to enable features that allow for a less trusted
interaction model between apps. See the bug for more details.

Note: this backport does not include the OBSCURED option since its
not needed for the security fix.

Test: atest libgui_test InputDispatcherDropInputFeatureTest
Bug: 197296414

Merged-In: I443741d5ab51a45d37fb865f11c433c436d96c1e
Change-Id: I443741d5ab51a45d37fb865f11c433c436d96c1e
diff --git a/services/surfaceflinger/Layer.cpp b/services/surfaceflinger/Layer.cpp
index 4e3ef24..bae242a 100644
--- a/services/surfaceflinger/Layer.cpp
+++ b/services/surfaceflinger/Layer.cpp
@@ -119,6 +119,7 @@
     mCurrentState.treeHasFrameRateVote = false;
     mCurrentState.fixedTransformHint = ui::Transform::ROT_INVALID;
     mCurrentState.isTrustedOverlay = false;
+    mCurrentState.dropInputMode = gui::DropInputMode::NONE;
 
     if (args.flags & ISurfaceComposerClient::eNoColorFill) {
         // Set an invalid color so there is no color fill.
@@ -2645,6 +2646,16 @@
     }
 }
 
+bool Layer::setDropInputMode(gui::DropInputMode mode) {
+    if (mCurrentState.dropInputMode == mode) {
+        return false;
+    }
+    mCurrentState.dropInputMode = mode;
+    mCurrentState.modified = true;
+    mCurrentState.inputInfoChanged = true;
+    setTransactionFlags(eTransactionNeeded);
+    return true;
+}
 // ---------------------------------------------------------------------------
 
 }; // namespace android