start to remove lockPixels from bitmapshader

src/core/SkBitmapProcShader.cpp

Index: src/core/SkBitmapProcShader.cpp
diff --git a/src/core/SkBitmapProcShader.cpp b/src/core/SkBitmapProcShader.cpp
index 3f657156f4f6f1d6333584a70e88905968d55167..ded1b7200938bb97a9d6dbe94d0eccc50f213408 100644
--- a/src/core/SkBitmapProcShader.cpp
+++ b/src/core/SkBitmapProcShader.cpp
@@ -80,24 +80,37 @@ bool SkBitmapProcShader::isOpaque() const {
     return fRawBitmap.isOpaque();
 }
 
+static bool valid_for_drawing(const SkBitmap& bm) {
+    if (0 == bm.width() || 0 == bm.height()) {
+        return false;   // nothing to draw
+    }
+    if (NULL == bm.pixelRef()) {
+        return false;   // no pixels to read
+    }
+    if (SkBitmap::kIndex8_Config == bm.config()) {
+        // ugh, I have to lock-pixels to inspect the colortable
+        SkAutoLockPixels alp(bm);
+        if (!bm.getColorTable()) {
+            return false;
+        }
+    }
+    return true;
+}
+
 bool SkBitmapProcShader::setContext(const SkBitmap& device,
                                     const SkPaint& paint,
                                     const SkMatrix& matrix) {
-    // do this first, so we have a correct inverse matrix
-    if (!this->INHERITED::setContext(device, paint, matrix)) {
+    if (!fRawBitmap.getTexture() && !valid_for_drawing(fRawBitmap)) {
         return false;
     }
 
-    fState.fOrigBitmap = fRawBitmap;
-    fState.fOrigBitmap.lockPixels();
-    if (!fState.fOrigBitmap.getTexture() && !fState.fOrigBitmap.readyToDraw()) {
-        fState.fOrigBitmap.unlockPixels();
-        this->INHERITED::endContext();
+    // do this first, so we have a correct inverse matrix
+    if (!this->INHERITED::setContext(device, paint, matrix)) {
         return false;
     }
 
+    fState.fOrigBitmap = fRawBitmap;
     if (!fState.chooseProcs(this->getTotalInverse(), paint)) {
-        fState.fOrigBitmap.unlockPixels();
         this->INHERITED::endContext();
         return false;
     }
@@ -147,7 +160,6 @@ bool SkBitmapProcShader::setContext(const SkBitmap& device,
 }
 
 void SkBitmapProcShader::endContext() {
-    fState.fOrigBitmap.unlockPixels();
     fState.endContext();
     this->INHERITED::endContext();
 }