hwui: add extension to support unpack operations in OpenGL ES 2.0

OpenGL ES 3.0+ lets us specify the row length for unpack operations
such as glTexSubImage2D(). This allows us to upload a sub-rectangle
of a texture. Also, the GL_EXT_unpack_subimage extension can also
support this feature in OpenGL ES 2.0

Change-Id: Id43c2c55c5eaefbace67087c955f0b4324fb2c35
Signed-off-by: xiaozhengdong <xiaozhengdong@xiaomi.com>
diff --git a/libs/hwui/Extensions.cpp b/libs/hwui/Extensions.cpp
index 84e7e65..25004b6 100644
--- a/libs/hwui/Extensions.cpp
+++ b/libs/hwui/Extensions.cpp
@@ -61,6 +61,7 @@
     mHasTiledRendering = hasGlExtension("GL_QCOM_tiled_rendering");
     mHas1BitStencil = hasGlExtension("GL_OES_stencil1");
     mHas4BitStencil = hasGlExtension("GL_OES_stencil4");
+    mHasUnpackSubImage = hasGlExtension("GL_EXT_unpack_subimage");
 
     // Query EGL extensions
     findExtensions(eglQueryString(eglGetCurrentDisplay(), EGL_EXTENSIONS), mEglExtensionList);
diff --git a/libs/hwui/Extensions.h b/libs/hwui/Extensions.h
index 25d4c5e..b3cc451 100644
--- a/libs/hwui/Extensions.h
+++ b/libs/hwui/Extensions.h
@@ -41,7 +41,7 @@
     inline bool has1BitStencil() const { return mHas1BitStencil; }
     inline bool has4BitStencil() const { return mHas4BitStencil; }
     inline bool hasNvSystemTime() const { return mHasNvSystemTime; }
-    inline bool hasUnpackRowLength() const { return mVersionMajor >= 3; }
+    inline bool hasUnpackRowLength() const { return mVersionMajor >= 3 || mHasUnpackSubImage; }
     inline bool hasPixelBufferObjects() const { return mVersionMajor >= 3; }
     inline bool hasOcclusionQueries() const { return mVersionMajor >= 3; }
     inline bool hasFloatTextures() const { return mVersionMajor >= 3; }
@@ -74,6 +74,7 @@
     bool mHas1BitStencil;
     bool mHas4BitStencil;
     bool mHasNvSystemTime;
+    bool mHasUnpackSubImage;
 
     int mVersionMajor;
     int mVersionMinor;