Remove support for gpu painting.

Fixes #3614.
Fixes #4683.
Fixes #7366.

components/gfx/paint_thread.rs

@@ -25,7 +25,6 @@ use paint_context::PaintContext;
 use profile_traits::mem::{self, ReportsChan};
 use profile_traits::time;
 use rand::{self, Rng};
-use skia::gl_context::GLContext;
 use std::borrow::ToOwned;
 use std::collections::HashMap;
 use std::mem as std_mem;
@@ -592,11 +591,7 @@ impl WorkerThreadProxy {
              font_cache_thread: FontCacheThread,
              time_profiler_chan: time::ProfilerChan)
              -> Vec<WorkerThreadProxy> {
-        let thread_count = if opts::get().gpu_painting {
-            1
-        } else {
-            opts::get().paint_threads
-        };
+        let thread_count = opts::get().paint_threads;
         (0..thread_count).map(|_| {
             let (from_worker_sender, from_worker_receiver) = channel();
             let (to_worker_sender, to_worker_receiver) = channel();
@@ -650,24 +645,6 @@ struct WorkerThread {
     native_display: Option<NativeDisplay>,
     font_context: Box<FontContext>,
     time_profiler_sender: time::ProfilerChan,
-    gl_context: Option<Arc<GLContext>>,
-}
-
-fn create_gl_context(native_display: Option<NativeDisplay>) -> Option<Arc<GLContext>> {
-    if !opts::get().gpu_painting {
-        return None;
-    }
-
-    match native_display {
-        Some(display) => {
-            let tile_size = opts::get().tile_size as i32;
-            GLContext::new(display.platform_display_data(), Size2D::new(tile_size, tile_size))
-        }
-        None => {
-            warn!("Could not create GLContext, falling back to CPU rasterization");
-            None
-        }
-    }
 }
 
 impl WorkerThread {
@@ -677,14 +654,12 @@ impl WorkerThread {
            font_cache_thread: FontCacheThread,
            time_profiler_sender: time::ProfilerChan)
            -> WorkerThread {
-        let gl_context = create_gl_context(native_display);
         WorkerThread {
             sender: sender,
             receiver: receiver,
             native_display: native_display,
             font_context: box FontContext::new(font_cache_thread.clone()),
             time_profiler_sender: time_profiler_sender,
-            gl_context: gl_context,
         }
     }
 
@@ -710,27 +685,6 @@ impl WorkerThread {
         }
     }
 
-    fn create_draw_target_for_layer_buffer(&self,
-                                           size: Size2D<i32>,
-                                           layer_buffer: &mut Box<LayerBuffer>)
-                                           -> DrawTarget {
-        match self.gl_context {
-            Some(ref gl_context) => {
-                match layer_buffer.native_surface.gl_rasterization_context(gl_context.clone()) {
-                    Some(rasterization_context) => {
-                        DrawTarget::new_with_gl_rasterization_context(rasterization_context,
-                                                                      SurfaceFormat::B8G8R8A8)
-                    }
-                    None => panic!("Could not create GLRasterizationContext for LayerBuffer"),
-                }
-            },
-            None => {
-                // A missing GLContext means we want CPU rasterization.
-                DrawTarget::new(BackendType::Skia, size, SurfaceFormat::B8G8R8A8)
-            }
-        }
-   }
-
     fn optimize_and_paint_tile(&mut self,
                                thread_id: usize,
                                mut tile: BufferRequest,
@@ -742,7 +696,7 @@ impl WorkerThread {
         let size = Size2D::new(tile.screen_rect.size.width as i32,
                                tile.screen_rect.size.height as i32);
         let mut buffer = self.create_layer_buffer(&mut tile, scale);
-        let draw_target = self.create_draw_target_for_layer_buffer(size, &mut buffer);
+        let draw_target = DrawTarget::new(BackendType::Skia, size, SurfaceFormat::B8G8R8A8);
 
         {
             // Build the paint context.
@@ -806,15 +760,13 @@ impl WorkerThread {
             }
         }
 
-        // Extract the texture from the draw target and place it into its slot in the buffer. If
-        // using CPU painting, upload it first.
-        if self.gl_context.is_none() {
-            draw_target.snapshot().get_data_surface().with_data(|data| {
-                buffer.native_surface.upload(native_display!(self), data);
-                debug!("painting worker thread uploading to native surface {}",
-                       buffer.native_surface.get_id());
-            });
-        }
+        // Extract the texture from the draw target and place it into its slot in the buffer.
+        // Upload it first.
+        draw_target.snapshot().get_data_surface().with_data(|data| {
+            buffer.native_surface.upload(native_display!(self), data);
+            debug!("painting worker thread uploading to native surface {}",
+                   buffer.native_surface.get_id());
+        });
 
         draw_target.finish();
         buffer
@@ -838,7 +790,7 @@ impl WorkerThread {
             rect: tile.page_rect,
             screen_pos: tile.screen_rect,
             resolution: scale,
-            painted_with_cpu: self.gl_context.is_none(),
+            painted_with_cpu: true,
             content_age: tile.content_age,
         }
     }