Move some work from backend onClear to base class clear

src/gpu/GrCommandBuilder.cpp

Index: src/gpu/GrCommandBuilder.cpp
diff --git a/src/gpu/GrCommandBuilder.cpp b/src/gpu/GrCommandBuilder.cpp
index 28c0cf2bdb5f58f466ea932732322c4ba7175f15..13191ad0279e08ec3ef0221179e4e1df7e2130a6 100644
--- a/src/gpu/GrCommandBuilder.cpp
+++ b/src/gpu/GrCommandBuilder.cpp
@@ -20,26 +20,14 @@ GrCommandBuilder* GrCommandBuilder::Create(GrGpu* gpu, bool reorder) {
 
 GrTargetCommands::Cmd* GrCommandBuilder::recordClear(const SkIRect* rect,
                                                      GrColor color,
-                                                     bool canIgnoreRect,
                                                      GrRenderTarget* renderTarget) {
     SkASSERT(renderTarget);
-
-    SkIRect r;
-    if (NULL == rect) {
-        // We could do something smart and remove previous draws and clears to
-        // the current render target. If we get that smart we have to make sure
-        // those draws aren't read before this clear (render-to-texture).
-        r.setLTRB(0, 0, renderTarget->width(), renderTarget->height());
-        rect = &r;
-    }
-
-    SkASSERT(canIgnoreRect || (rect->fLeft <= rect->fRight && rect->fTop <= rect->fBottom));
+    SkASSERT(rect->fLeft <= rect->fRight && rect->fTop <= rect->fBottom);
 
     Clear* clr = GrNEW_APPEND_TO_RECORDER(*this->cmdBuffer(), Clear, (renderTarget));
     GrColorIsPMAssert(color);
     clr->fColor = color;
     clr->fRect = *rect;
-    clr->fCanIgnoreRect = canIgnoreRect;
     return clr;
 }