This is initial API support required for enabling SurfaceTexture backed zero-copy for Android

ui/android/java/src/org/chromium/ui/gl/SurfaceTexturePlatformWrapper.java

Index: ui/android/java/src/org/chromium/ui/gl/SurfaceTexturePlatformWrapper.java
diff --git a/ui/android/java/src/org/chromium/ui/gl/SurfaceTexturePlatformWrapper.java b/ui/android/java/src/org/chromium/ui/gl/SurfaceTexturePlatformWrapper.java
index 53d33036edebd785726c59dd42110a40fa6b1610..f44e151baf45e24d2b2f19836192ac3c741d1bfe 100644
--- a/ui/android/java/src/org/chromium/ui/gl/SurfaceTexturePlatformWrapper.java
+++ b/ui/android/java/src/org/chromium/ui/gl/SurfaceTexturePlatformWrapper.java
@@ -21,8 +21,8 @@ class SurfaceTexturePlatformWrapper {
     private static final String TAG = "SurfaceTexturePlatformWrapper";
 
     @CalledByNative
-    private static SurfaceTexture create(int textureId) {
-        return new SurfaceTexture(textureId);
+    private static SurfaceTexture create(int textureId, boolean singleBufferMode) {
+        return new SurfaceTexture(textureId, singleBufferMode);

[bulach, 2014/03/10 12:32:31]

I think this will break quite a few bots not on KitKat :(

at a minimum, it needs to be guarded with Build.VERSION.SDK_INT >=
Build.VERSION_CODES.KITKAT.

this is going to be tricky to implement down in C++.
what are the semantics there?
should we fail when trying singleBufferMode before KK?
should we gracefully fallback?
how about the releaseTextImage, would it fail or fallback?

some options:
- have two explicit factory methods, "create(int textureId)" and
"createSingleBuffer(int textureId)".
- this would then translate to two constructors (or better, factory methods) in
the C++ side..

alternatively:
- have a subclass in C++, SingleBufferSurfaceTexture, deriving from
SurfaceTexture and introducing the ReleaseTextImage() method.. then, it'd be
easier to spot that it's only used where actually available..


to be clear: the java part is private and an internal detail of the C++ side..
I'm not too concerned about this.
my concern is actually on the C++ side, and making sure that we won't start
sprinkling version checks all over the place there...

[reveman, 2014/03/10 13:33:05]

Right. Forgot that this is only available since kitkat.
Silent fallback can be a problem. Let's not do that.
Fail. We should probably have a DCHECK in C++ code to guard against it being
used on non-single buffered surface textures.
Either is fine with me. Maybe prefer the two ctor approach a bit as it matches
the Android Java API for SurfaceTexture better.

I guess another alternative is adding:
static bool IsSingleBufferModeSupported()
or just making it single_buffer_mode=true illegal unless on kitkat and later and
push the responsibility of checking
base::android::BuildInfo::GetInstance()->sdk_int() to the client.

[bulach, 2014/03/10 13:47:49]

thanks reveman! of all alternatives, I think your proposal of "static bool
IsSingleBufferModeSupported()" would be my preferred :)
that, and making the C++ constructor private and having explicitly named factory
functions in c++...
the reason being that further down line, it'll probably be easier for reviewers
to ensure things like:

if (SurfaceTexture::IsSingleBufferModeSupported())
  ... SurfaceTexture::CreateSingleBufferModeTexture(...);

than:
if (BuildInfo...sdk_int()...)
  ... new SurfaceTexture::SurfaceTexture(..., true);


I think we're in the same page here, but just want to be more explicit. :)

oh, and of course, "CreateSingleBufferModeTexture()" should have a comment
saying "this must only be called if |IsSingleBufferModeSupported()|", and a
DCHECK for that.

the java part also needs to be split, since this ctor with two params is not
available pre kk..

     }
 
     @CalledByNative
@@ -48,6 +48,11 @@ class SurfaceTexturePlatformWrapper {
     }
 
     @CalledByNative
+    private static void releaseTexImage(SurfaceTexture surfaceTexture) {
+        surfaceTexture.releaseTexImage();

[bulach, 2014/03/10 12:32:31]

assert Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT;

+    }
+
+    @CalledByNative
     private static void setDefaultBufferSize(SurfaceTexture surfaceTexture, int width,
             int height) {
         surfaceTexture.setDefaultBufferSize(width, height);