Record SkPicture with correct LCD text setting.

cc/layers/content_layer_client.h

Index: cc/layers/content_layer_client.h
diff --git a/cc/layers/content_layer_client.h b/cc/layers/content_layer_client.h
index 8271cd5e27f1711d2e2e7ba8ee38c2b39d82c7ea..14c276e850a749669986f11a0775f175d7805fcd 100644
--- a/cc/layers/content_layer_client.h
+++ b/cc/layers/content_layer_client.h
@@ -25,12 +25,13 @@ class CC_EXPORT ContentLayerClient {
 
   virtual void PaintContents(SkCanvas* canvas,
                              const gfx::Rect& clip,
+                             bool can_paint_lcd_text,
                              gfx::RectF* opaque,
                              GraphicsContextStatus gc_status) = 0;
 
-  // Called by the content layer during the update phase.
-  // If the client paints LCD text, it may want to invalidate the layer.
-  virtual void DidChangeLayerCanUseLCDText() = 0;
+  // If true the layer may need to invalidate itself when LCD text status
+  // changes.
+  virtual bool PaintsLCDText() const = 0;

[enne (OOO), 2014/06/06 16:59:32]

Please don't change this.  It should be up to the layer client whether or not
the layer should be invalidated or not.  The ui compositor can't repaint layers
and doesn't want these extra invalidations.

[alokp, 2014/06/06 19:15:05]

That is what this function is supposed to prevent. The ui compositor layers are
NOT invalidated. The layers are only invalidated if this function returns true.

[alokp, 2014/06/06 22:05:40]

I realized that there is no test for this. I have added it in
LayerTreeHostTestLCDText.

[enne (OOO), 2014/06/06 22:20:59]

Sure, but this also means that ui layers can no longer say that they want LCD
text if they don't want to be invalidated.

Maybe piman can chime in here?

[alokp, 2014/06/06 22:31:27]

But if you actually paint LCD text and it is no longer allowed, the layer should
be invalidated. Otherwise it will look ugly. Do UI layers paint lcd even when it
is not allowed?

[alokp, 2014/06/10 17:18:59]

piman: Do you see any issues with modifying this API. The ui::layer will still
not be invalidated - it used to ignore this callback anyway. Modifying this API
allows me to avoid tracking the LCD state at two places - ContentLayer and
WebContentLayerImpl. IMO this is much cleaner.

[piman, 2014/06/10 22:57:45]

I can't tell for sure if that happens.
What is true though is that there are states where the UI layers want to avoid
invalidations because they can't repaint any more (during closing animations and
the like). When that is the case, it'd be preferable to have somewhat incorrect
LCD text rather than black.

[alokp, 2014/06/10 23:33:47]

AFAICT in the current world ui::Layer is never invalidated due to change in LCD
text status. This patch does not change that. I guess I do not see how ui::Layer
may get invalidated. Are you worried about the case in future when
ui::Layer::PaintsLCDText may want to return true?

 
   // If true the layer may skip clearing the background before rasterizing,
   // because it will cover any uncleared data with content.