Don't enable HDCP again if it is active

ui/display/chromeos/display_configurator.cc

Index: ui/display/chromeos/display_configurator.cc
diff --git a/ui/display/chromeos/display_configurator.cc b/ui/display/chromeos/display_configurator.cc
index 19e122566e8412af5a1c2d3a5670a1acaeecf42e..08a58aa05ec3238a0bc895e9c92ddc8f4eff2212 100644
--- a/ui/display/chromeos/display_configurator.cc
+++ b/ui/display/chromeos/display_configurator.cc
@@ -251,12 +251,19 @@ bool DisplayConfigurator::ApplyProtections(const ContentProtections& requests) {
       case DISPLAY_CONNECTION_TYPE_DISPLAYPORT:
       case DISPLAY_CONNECTION_TYPE_DVI:
       case DISPLAY_CONNECTION_TYPE_HDMI: {
-        HDCPState new_desired_state =
-            (all_desired & CONTENT_PROTECTION_METHOD_HDCP) ?
-                HDCP_STATE_DESIRED : HDCP_STATE_UNDESIRED;
-        if (!native_display_delegate_->SetHDCPState(*it->display,
-                                                    new_desired_state))
+        HDCPState current_state;
+        if (!native_display_delegate_->GetHDCPState(*it->display,

[dnicoara, 2014/09/19 15:57:53]

Would you mind adding a comment here to explain why this is necessary? I'm
afraid someone will try to optimize this out in a refactor.

[kcwu, 2014/09/23 05:43:22]

I am not sure what you mean. I added one more sentence in line 260. Please take
a look.

[dnicoara, 2014/09/23 13:35:44]

Awesome! I'm thinking something along the lines "Need to poll the driver for
updates since other applications may have updated the state". Something along
the lines of your explanation in message #6.

[kcwu, 2014/09/24 14:57:44]

Done.

+                                                    &current_state))
           return false;
+        bool current_desired = (current_state != HDCP_STATE_UNDESIRED);
+        bool new_desired = (all_desired & CONTENT_PROTECTION_METHOD_HDCP);
+        // Don't enable again if HDCP is already active.
+        if (current_desired != new_desired) {
+          HDCPState new_state =
+              new_desired ? HDCP_STATE_DESIRED : HDCP_STATE_UNDESIRED;
+          if (!native_display_delegate_->SetHDCPState(*it->display, new_state))
+            return false;
+        }
         break;
       }
       case DISPLAY_CONNECTION_TYPE_INTERNAL: