drm_hwcomposer: Remove unimplemented display brightness code

This is not implemented in HWC3, so remove related code. It can be added
back when support for display brightness is implemented.

Change-Id: If7d0a111b22815e92e76a2506400e172baa1a60c
Signed-off-by: Drew Davenport <ddavenport@google.com>
diff --git a/hwc3/ComposerClient.cpp b/hwc3/ComposerClient.cpp
index c26d851..848c587 100644
--- a/hwc3/ComposerClient.cpp
+++ b/hwc3/ComposerClient.cpp
@@ -602,9 +602,7 @@
     DispatchLayerCommand(command.display, layer_cmd);
   }
 
-  if (command.brightness) {
-    ExecuteSetDisplayBrightness(command.display, *command.brightness);
-  }
+  // TODO: Implement support for display brightness.
   if (command.colorTransformMatrix) {
     ExecuteSetDisplayColorTransform(command.display,
                                     *command.colorTransformMatrix);
@@ -1258,20 +1256,6 @@
   return err;
 }
 
-void ComposerClient::ExecuteSetDisplayBrightness(
-    uint64_t display_id, const DisplayBrightness& command) {
-  auto* display = GetDisplay(display_id);
-  if (display == nullptr) {
-    cmd_result_writer_->AddError(hwc3::Error::kBadDisplay);
-    return;
-  }
-
-  auto error = Hwc2toHwc3Error(
-      display->SetDisplayBrightness(command.brightness));
-  if (error != hwc3::Error::kNone) {
-    cmd_result_writer_->AddError(error);
-  }
-}
 void ComposerClient::ExecuteSetDisplayColorTransform(
     uint64_t display_id, const std::vector<float>& matrix) {
   auto* display = GetDisplay(display_id);
diff --git a/hwc3/ComposerClient.h b/hwc3/ComposerClient.h
index 45607fe..91a0be0 100644
--- a/hwc3/ComposerClient.h
+++ b/hwc3/ComposerClient.h
@@ -165,8 +165,6 @@
 
   // Display commands
   void ExecuteDisplayCommand(const DisplayCommand& command);
-  void ExecuteSetDisplayBrightness(uint64_t display_id,
-                                   const DisplayBrightness& command);
   void ExecuteSetDisplayColorTransform(uint64_t display_id,
                                        const std::vector<float>& matrix);
   void ExecuteSetDisplayClientTarget(uint64_t display_id,