Implement Virtual Display class for Android.

ui/android/java/src/org/chromium/ui/display/DisplayAndroidManager.java

Index: ui/android/java/src/org/chromium/ui/display/DisplayAndroidManager.java
diff --git a/ui/android/java/src/org/chromium/ui/display/DisplayAndroidManager.java b/ui/android/java/src/org/chromium/ui/display/DisplayAndroidManager.java
index 6175f940303e80ee9df4afbc5c65cb358a2d988d..ffa765436b6d4461fd4f54f9cafa2c4cea5eee9d 100644
--- a/ui/android/java/src/org/chromium/ui/display/DisplayAndroidManager.java
+++ b/ui/android/java/src/org/chromium/ui/display/DisplayAndroidManager.java
@@ -112,7 +112,7 @@ import org.chromium.ui.gfx.DeviceDisplayInfo;
         @Override
         public void onConfigurationChanged(Configuration newConfig) {
             updateDeviceDisplayInfo();
-            mIdMap.get(mMainSdkDisplayId).updateFromDisplay(
+            ((DisplayAndroidImpl) mIdMap.get(mMainSdkDisplayId)).updateFromDisplay(
                     getDefaultDisplayForContext(getContext()));
         }
 
@@ -171,7 +171,7 @@ import org.chromium.ui.gfx.DeviceDisplayInfo;
         @Override
         public void onDisplayChanged(int sdkDisplayId) {
             updateDeviceDisplayInfo();
-            DisplayAndroid displayAndroid = mIdMap.get(sdkDisplayId);
+            DisplayAndroidImpl displayAndroid = (DisplayAndroidImpl) mIdMap.get(sdkDisplayId);
             if (displayAndroid != null) {
                 displayAndroid.updateFromDisplay(getDisplayManager().getDisplay(sdkDisplayId));
             }
@@ -180,10 +180,15 @@ import org.chromium.ui.gfx.DeviceDisplayInfo;
 
     private static DisplayAndroidManager sDisplayAndroidManager;
 
+    // Real displays on Android start at ID 0, so to avoid any overlap, start virtual displays at
+    // a much higher number.
+    private static final int VIRTUAL_DISPLAY_ID_BEGIN = 1000;

[boliu, 2016/11/28 15:53:31]

I need we need to double check how android generates its display IDs.

If it's internally also keeping a counter like this, then 1000 isn't an
impossibly high number to reach. But if it's immediately re-using empty slots
starting from 0 or something, then it's fine.

Can you double check and report back? "Settings->Developer options->Simulate
secondary display" should be good enough

[mthiesse, 2016/11/28 19:16:42]

Android effectively does what I'm doing here, but starts at 1. They never re-use
slots, and both virtual and physical displays are assigned IDs in the same way -
search for "assignDisplayIdLocked" in android source to verify. This is true for
at least as far back as jellybean.

I'll up it to something more impossibly high.

+
     private long mNativePointer;
     private int mMainSdkDisplayId;
     private SparseArray<DisplayAndroid> mIdMap;
     private DisplayListenerBackend mBackend;
+    private int mNextVirtualDisplayId = VIRTUAL_DISPLAY_ID_BEGIN;
 
     @SuppressFBWarnings("LI_LAZY_INIT_UPDATE_STATIC")
     /* package */ static DisplayAndroidManager getInstance() {
@@ -278,16 +283,32 @@ import org.chromium.ui.gfx.DeviceDisplayInfo;
 
     private DisplayAndroid addDisplay(Display display) {
         int sdkDisplayId = display.getDisplayId();
-        DisplayAndroid displayAndroid = new DisplayAndroid(display);
+        DisplayAndroidImpl displayAndroid = new DisplayAndroidImpl(display);
         mIdMap.put(sdkDisplayId, displayAndroid);
 
         displayAndroid.updateFromDisplay(display);
         return displayAndroid;
     }
 
+    /* package */ int getNextVirtualDisplayId() {

[boliu, 2016/11/28 15:53:31]

nit: maybe generating this ID can happen in addVirtualDisplay, then one less
back and forth call, and can also assert the generated id isn't already in the
map

also can we crash hard if the IDs ever collide, in both ways? if this is buggy,
we want to know immediately

[mthiesse, 2016/11/28 19:16:42]

Done.

+        return mNextVirtualDisplayId++;
+    }
+
+    /* package */ void addVirtualDisplay(VirtualDisplayAndroid display) {
+        mIdMap.put(display.getDisplayId(), display);

[boliu, 2016/11/28 15:53:31]

should this immediately create the native side display? or maybe
createVirtualDisplay should take all the params, so it's impossible for client
to leave things in an inconsistent state

[mthiesse, 2016/11/28 19:16:42]

Done.

+    }
+
+    /* package */ void removeVirtualDisplay(VirtualDisplayAndroid display) {
+        DisplayAndroid displayAndroid = mIdMap.get(display.getDisplayId());
+        assert displayAndroid == display;
+
+        if (mNativePointer != 0) nativeRemoveDisplay(mNativePointer, display.getDisplayId());
+        mIdMap.remove(display.getDisplayId());
+    }
+
     /* package */ void updateDisplayOnNativeSide(DisplayAndroid displayAndroid) {
         if (mNativePointer == 0) return;
-        nativeUpdateDisplay(mNativePointer, displayAndroid.getSdkDisplayId(),
+        nativeUpdateDisplay(mNativePointer, displayAndroid.getDisplayId(),
                 displayAndroid.getPhysicalDisplayWidth(), displayAndroid.getPhysicalDisplayHeight(),
                 displayAndroid.getDisplayWidth(), displayAndroid.getDisplayHeight(),
                 displayAndroid.getDipScale(), displayAndroid.getRotationDegrees(),