fix [2315900] Monochrome camera preview screen after launching camera

this was introduced by a recent change. when we try to figure out the size of
the yuv->rgb temporary buffer, the output resolution has not been computed yet
and an invalid buffer size is used. most of the time the allocation fails
and the system reverts to "standard" GL will uses onle the Y plane.

the allocation of the temporary buffer is moved to onDraw(), the first
time it is called, by that time, the window is positioned properly.
diff --git a/libs/surfaceflinger/LayerBuffer.cpp b/libs/surfaceflinger/LayerBuffer.cpp
index 137c5c0..2ff6167 100644
--- a/libs/surfaceflinger/LayerBuffer.cpp
+++ b/libs/surfaceflinger/LayerBuffer.cpp
@@ -364,43 +364,6 @@
         return;
     }
 
-    if (mLayer.mBlitEngine) {
-        // create our temporary buffer and corresponding EGLImageKHR.
-        // note that the size of this buffer doesn't really matter,
-        // the final image will always be drawn with proper aspect ratio.
-
-        int w = layer.mTransformedBounds.width();
-        int h = layer.mTransformedBounds.height();
-        if (buffers.w * h != buffers.h * w) {
-            int t = w; w = h; h = t;
-        }
-        if (buffers.w * h == buffers.h * w) {
-            // same pixel area, don't use filtering
-            layer.mUseLinearFiltering = false;
-        }
-
-        mTempGraphicBuffer.clear();
-        mTempGraphicBuffer = new GraphicBuffer(
-                w, h, HAL_PIXEL_FORMAT_RGB_565,
-                GraphicBuffer::USAGE_HW_TEXTURE |
-                GraphicBuffer::USAGE_HW_2D);
-
-        if (mTempGraphicBuffer->initCheck() == NO_ERROR) {
-            NativeBuffer& dst(mTempBuffer);
-            dst.img.w = mTempGraphicBuffer->getStride();
-            dst.img.h = h;
-            dst.img.format = mTempGraphicBuffer->getPixelFormat();
-            dst.img.handle = (native_handle_t *)mTempGraphicBuffer->handle;
-            dst.img.base = 0;
-            dst.crop.l = 0;
-            dst.crop.t = 0;
-            dst.crop.r = w;
-            dst.crop.b = h;
-        } else {
-            mTempGraphicBuffer.clear();
-        }
-    }
-
     mBufferHeap = buffers;
     mLayer.setNeedsBlending((info.h_alpha - info.l_alpha) > 0);    
     mBufferSize = info.getScanlineSize(buffers.hor_stride)*buffers.ver_stride;
@@ -492,18 +455,7 @@
         copybit_device_t* copybit = mLayer.mBlitEngine;
         if (copybit) {
             // create our EGLImageKHR the first time
-            if (mTexture.image == EGL_NO_IMAGE_KHR) {
-                err = NO_MEMORY;
-                if (mTempGraphicBuffer!=0) {
-                    err = mLayer.initializeEglImage(
-                            mTempGraphicBuffer, &mTexture);
-                    // once the EGLImage has been created (whether it fails
-                    // or not) we don't need the graphic buffer reference
-                    // anymore.
-                    mTempGraphicBuffer.clear();
-                }
-            }
-
+            err = initTempBuffer();
             if (err == NO_ERROR) {
                 // NOTE: Assume the buffer is allocated with the proper USAGE flags
                 const NativeBuffer& dst(mTempBuffer);
@@ -542,6 +494,72 @@
     mLayer.drawWithOpenGL(clip, mTexture);
 }
 
+status_t LayerBuffer::BufferSource::initTempBuffer() const
+{
+    // figure out the size we need now
+    const ISurface::BufferHeap& buffers(mBufferHeap);
+    uint32_t w = mLayer.mTransformedBounds.width();
+    uint32_t h = mLayer.mTransformedBounds.height();
+    if (buffers.w * h != buffers.h * w) {
+        int t = w; w = h; h = t;
+    }
+
+    if (mTexture.image != EGL_NO_IMAGE_KHR) {
+        // we have an EGLImage, make sure the needed size didn't change
+        if (w!=mTexture.width || h!= mTexture.height) {
+            // delete the EGLImage and texture
+            EGLDisplay dpy(mLayer.mFlinger->graphicPlane(0).getEGLDisplay());
+            glDeleteTextures(1, &mTexture.name);
+            eglDestroyImageKHR(dpy, mTexture.image);
+            Texture defaultTexture;
+            mTexture = defaultTexture;
+            mTempGraphicBuffer.clear();
+        } else {
+            // we're good, we have an EGLImageKHR and it's (still) the
+            // right size
+            return NO_ERROR;
+        }
+    }
+
+    // figure out if we need linear filtering
+    if (buffers.w * h == buffers.h * w) {
+        // same pixel area, don't use filtering
+        mLayer.mUseLinearFiltering = false;
+    }
+
+    // Allocate a temporary buffer and create the corresponding EGLImageKHR
+
+    status_t err;
+    mTempGraphicBuffer.clear();
+    mTempGraphicBuffer = new GraphicBuffer(
+            w, h, HAL_PIXEL_FORMAT_RGB_565,
+            GraphicBuffer::USAGE_HW_TEXTURE |
+            GraphicBuffer::USAGE_HW_2D);
+
+    err = mTempGraphicBuffer->initCheck();
+    if (err == NO_ERROR) {
+        NativeBuffer& dst(mTempBuffer);
+        dst.img.w = mTempGraphicBuffer->getStride();
+        dst.img.h = h;
+        dst.img.format = mTempGraphicBuffer->getPixelFormat();
+        dst.img.handle = (native_handle_t *)mTempGraphicBuffer->handle;
+        dst.img.base = 0;
+        dst.crop.l = 0;
+        dst.crop.t = 0;
+        dst.crop.r = w;
+        dst.crop.b = h;
+
+        err = mLayer.initializeEglImage(
+                mTempGraphicBuffer, &mTexture);
+        // once the EGLImage has been created (whether it fails
+        // or not) we don't need the graphic buffer reference
+        // anymore.
+        mTempGraphicBuffer.clear();
+    }
+
+    return err;
+}
+
 // ---------------------------------------------------------------------------
 
 LayerBuffer::OverlaySource::OverlaySource(LayerBuffer& layer,
diff --git a/libs/surfaceflinger/LayerBuffer.h b/libs/surfaceflinger/LayerBuffer.h
index 1abb103..2ca63ac 100644
--- a/libs/surfaceflinger/LayerBuffer.h
+++ b/libs/surfaceflinger/LayerBuffer.h
@@ -130,13 +130,14 @@
         virtual bool transformed() const;
         virtual void destroy() { }
     private:
+        status_t initTempBuffer() const;
         mutable Mutex                   mBufferSourceLock;
         sp<Buffer>                      mBuffer;
         status_t                        mStatus;
         ISurface::BufferHeap            mBufferHeap;
         size_t                          mBufferSize;
         mutable LayerBase::Texture      mTexture;
-        NativeBuffer                    mTempBuffer;
+        mutable NativeBuffer            mTempBuffer;
         mutable sp<GraphicBuffer>       mTempGraphicBuffer;
     };