Move some parts of onReadPixels up to GrGpu readPixels.

src/gpu/GrGpu.cpp

Index: src/gpu/GrGpu.cpp
diff --git a/src/gpu/GrGpu.cpp b/src/gpu/GrGpu.cpp
index c7137ef6918fb67141d0eee2b3840fbc114e15c9..c3501bc99687503c24ab12339bed9f5e6c64bd24 100644
--- a/src/gpu/GrGpu.cpp
+++ b/src/gpu/GrGpu.cpp
@@ -17,6 +17,7 @@
 #include "GrResourceCache.h"
 #include "GrRenderTargetPriv.h"
 #include "GrStencilAttachment.h"
+#include "GrSurfacePriv.h"
 #include "GrVertexBuffer.h"
 #include "GrVertices.h"
 
@@ -292,7 +293,30 @@ bool GrGpu::readPixels(GrSurface* surface,
                        GrPixelConfig config, void* buffer,
                        size_t rowBytes) {
     this->handleDirtyContext();
-    return this->onReadPixels(surface, left, top, width, height, config, buffer, rowBytes);
+
+    // We cannot read pixels into a compressed buffer

[egdaniel, 2015/07/30 18:00:49]

It can be argued this one is dependent on the backend, but I don't see a reason
we can't just say we don't support reading into a compressed buffer in general.

[bsalomon, 2015/07/30 18:27:22]

If we're going to do this then we should also move the corresponding code in
onGetReadPixelsInfo to getReadPixelsInfo.

[egdaniel, 2015/07/30 18:47:34]

Done.

+    if (GrPixelConfigIsCompressed(config)) {
+        return false;
+    }
+
+    size_t bpp = GrBytesPerPixel(config);
+    if (!GrSurfacePriv::AdjustReadPixelParams(surface->width(), surface->height(), bpp,
+                                              &left, &top, &width, &height,
+                                              &buffer,
+                                              &rowBytes)) {
+        return false;
+    }
+
+    size_t tightRowBytes = bpp * width;
+    if (0 == rowBytes) {

[bsalomon, 2015/07/30 18:27:22]

AdjustReadPixelParams already does this (sets rowBytes to tight if it's zero).
So this can be removed.

[egdaniel, 2015/07/30 18:47:34]

Done.

+        rowBytes = tightRowBytes;
+    }
+
+    return this->onReadPixels(surface,
+                              left, top, width, height,
+                              config, buffer,
+                              rowBytes ? rowBytes : tightRowBytes,
+                              tightRowBytes);
 }
 
 bool GrGpu::writePixels(GrSurface* surface,