Limit the number of WebGL contexts that are active at any given time

Source/core/platform/graphics/gpu/DrawingBuffer.h

Index: Source/core/platform/graphics/gpu/DrawingBuffer.h
diff --git a/Source/core/platform/graphics/gpu/DrawingBuffer.h b/Source/core/platform/graphics/gpu/DrawingBuffer.h
index 1d8c2b7a98cd3c69ffc81bcfd2a41f7f6ff26caf..7087674ee587c06f7d4c171a22e343f03fe1984e 100644
--- a/Source/core/platform/graphics/gpu/DrawingBuffer.h
+++ b/Source/core/platform/graphics/gpu/DrawingBuffer.h
@@ -152,6 +152,10 @@ private:
     // Calculates the difference in pixels between the current buffer size and the proposed size.
     int pixelDelta(const IntSize& size);
 
+    // Given the desired buffer size, provides the largest dimensions that will fit in the pixel budget
+    // Returns true if the buffer will only fit if the oldest WebGL context is forcibly lost
+    IntSize adjustSizeWithContextEviction(const IntSize&, bool& evictContext);
+
     PreserveDrawingBuffer m_preserveDrawingBuffer;
     bool m_scissorEnabled;
     Platform3DObject m_texture2DBinding;