Implement difference clip rects with window rectangles

src/gpu/GrCaps.cpp

Index: src/gpu/GrCaps.cpp
diff --git a/src/gpu/GrCaps.cpp b/src/gpu/GrCaps.cpp
index 19ef38c49d244fe226e47e3232fe5457ed1e8f29..622c6855fae0ad93e29fd05c4fc6c62a0b65df45 100644
--- a/src/gpu/GrCaps.cpp
+++ b/src/gpu/GrCaps.cpp
@@ -7,6 +7,7 @@
 
 #include "GrCaps.h"
 #include "GrContextOptions.h"
+#include "GrWindowRectangles.h"
 
 GrShaderCaps::GrShaderCaps() {
     fShaderDerivativeSupport = false;
@@ -131,6 +132,7 @@ GrCaps::GrCaps(const GrContextOptions& options) {
 }
 
 void GrCaps::applyOptionsOverrides(const GrContextOptions& options) {
+    this->onApplyOptionsOverrides(options);
     fMaxTextureSize = SkTMin(fMaxTextureSize, options.fMaxTextureSizeOverride);
     // If the max tile override is zero, it means we should use the max texture size.
     if (!options.fMaxTileSizeOverride || options.fMaxTileSizeOverride > fMaxTextureSize) {
@@ -138,7 +140,9 @@ void GrCaps::applyOptionsOverrides(const GrContextOptions& options) {
     } else {
         fMaxTileSize = options.fMaxTileSizeOverride;
     }
-    this->onApplyOptionsOverrides(options);
+    if (fMaxWindowRectangles > GrWindowRectangles::kMaxWindows) {
+        fMaxWindowRectangles = GrWindowRectangles::kMaxWindows;

[csmartdalton, 2016/08/17 18:24:06]

We still cap. The cap just got moved here instead. (To the platform-independent
part. i.e. this will cap vulkan too)

kMaxWindows is 16. But I agree your suggestion of 8 makes more sense. Lets drop
to 8 and always increase later if needed.

+    }
 }
 
 static SkString map_flags_to_string(uint32_t flags) {