histogram: enable histogram events

Use the sde-drm library to add the properties that generated
histogram interrupts into the atomic commital. This enables
the generation of the histogram events once the vndservice call
listed below is made. HWC hooks into control to follow
(i.e. currently HWC cannot turn feature on).

Change-Id: I9bbeed3c76a418dabe61742742de37af0ab5151e
Signed-off-by: Kevin DuBois <kevindubois@google.com>
Signed-off-by: Lakshmi Narayana Kalavala <lkalaval@codeaurora.org>
diff --git a/composer/hwc_display_builtin.cpp b/composer/hwc_display_builtin.cpp
index ac801a7..d50173b 100644
--- a/composer/hwc_display_builtin.cpp
+++ b/composer/hwc_display_builtin.cpp
@@ -963,7 +963,9 @@
   vndservice_sampling_vote = enabled;
   if (api_sampling_vote || vndservice_sampling_vote) {
     histogram.start();
+    display_intf_->colorSamplingOn();
   } else {
+    display_intf_->colorSamplingOff();
     histogram.stop();
   }
   return HWC2::Error::None;
@@ -986,9 +988,12 @@
   auto start = api_sampling_vote || vndservice_sampling_vote;
   if (start && max_frames == 0) {
     histogram.start();
+    display_intf_->colorSamplingOn();
   } else if (start) {
     histogram.start(max_frames);
+    display_intf_->colorSamplingOn();
   } else {
+    display_intf_->colorSamplingOff();
     histogram.stop();
   }
   return HWC2::Error::None;