Normalize GL_UNPACK_ALIGNMENT

Several places were setting GL_UNPACK_ALIGNMENT
unneccessarily, whereas other places were assuming an
unpack alignment of 1. Since we never actually
do explicit row-alignment, set GL_UNPACK_ALIGNMENT
to 1 at context creation time and never change it

Bug: 26584230

Also turns on aggressive glGetError checking to
better catch potential problem zones

Change-Id: I190c8f0f0494a7f046d5ed769405c75d363be59a
diff --git a/libs/hwui/PixelBuffer.cpp b/libs/hwui/PixelBuffer.cpp
index 9624726..6df994c 100644
--- a/libs/hwui/PixelBuffer.cpp
+++ b/libs/hwui/PixelBuffer.cpp
@@ -20,6 +20,7 @@
 #include "Extensions.h"
 #include "Properties.h"
 #include "renderstate/RenderState.h"
+#include "utils/GLUtils.h"
 
 #include <utils/Log.h>
 
@@ -112,14 +113,10 @@
     if (mAccessMode == kAccessMode_None) {
         mCaches.pixelBufferState().bind(mBuffer);
         mMappedPointer = (uint8_t*) glMapBufferRange(GL_PIXEL_UNPACK_BUFFER, 0, getSize(), mode);
-#if DEBUG_OPENGL
-        if (!mMappedPointer) {
-            GLenum status = GL_NO_ERROR;
-            while ((status = glGetError()) != GL_NO_ERROR) {
-                ALOGE("Could not map GPU pixel buffer: 0x%x", status);
-            }
+        if (CC_UNLIKELY(!mMappedPointer)) {
+            GLUtils::dumpGLErrors();
+            LOG_ALWAYS_FATAL("Failed to map PBO");
         }
-#endif
         mAccessMode = mode;
     }