i965: When an RB gets a new region, clear the old from the state cache.

This prevents memory usage explosion in blender due to the state cache
hanging on to old fake frontbuffer regions.  Sigh at blender still
using frontbuffer rendering.

Bug #24119.

src/mesa/drivers/dri/intel/intel_fbo.c

@@ -42,7 +42,9 @@
 #include "intel_fbo.h"
 #include "intel_mipmap_tree.h"
 #include "intel_regions.h"
-
+#ifndef I915
+#include "brw_state.h"
+#endif
 
 #define FILE_DEBUG_FLAG DEBUG_FBO
 
@@ -280,7 +282,8 @@ intel_nop_alloc_storage(GLcontext * ctx, struct gl_renderbuffer *rb,
 
 
 void
-intel_renderbuffer_set_region(struct intel_renderbuffer *rb,
+intel_renderbuffer_set_region(struct intel_context *intel,
+			      struct intel_renderbuffer *rb,
 			      struct intel_region *region)
 {
    struct intel_region *old;
@@ -288,6 +291,12 @@ intel_renderbuffer_set_region(struct intel_renderbuffer *rb,
    old = rb->region;
    rb->region = NULL;
    intel_region_reference(&rb->region, region);
+#ifndef I915
+   if (old) {
+      brw_state_cache_bo_delete(&brw_context(&intel->ctx)->surface_cache,
+				old->buffer);
+   }
+#endif
    intel_region_release(&old);
 }