Migrate from MathUtil::inverse() to gfx::Transform::GetInverse()

cc/layer_tree_host_impl.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/layer_tree_host_impl.h"
 
 #include <algorithm>
 
 #include "base/basictypes.h"
 #include "base/debug/trace_event.h"
@@ skipping 473 matching lines @@
                           targetRenderPass->shared_quad_state_list,
                           rootLayer,
                           occlusionTracker,
                           rootLayer->showDebugBorders(),
                           forSurface);
 
     // Manually create the quad state for the gutter quads, as the root layer
     // doesn't have any bounds and so can't generate this itself.
     // FIXME: Make the gutter quads generated by the solid color layer (make it smarter about generating quads to fill unoccluded areas).
 
-    DCHECK(rootLayer->screenSpaceTransform().IsInvertible());
-
     gfx::Rect rootTargetRect = rootLayer->renderSurface()->contentRect();
     float opacity = 1;
     SharedQuadState* sharedQuadState = quadCuller.useSharedQuadState(SharedQuadState::Create());
     sharedQuadState->SetAll(rootLayer->drawTransform(),
                             rootTargetRect,
                             rootTargetRect,
                             rootTargetRect,
                             false,
                             opacity);
 
     AppendQuadsData appendQuadsData;
-    gfx::Transform transformToLayerSpace = MathUtil::inverse(rootLayer->screenSpaceTransform());
+
+    gfx::Transform transformToLayerSpace(gfx::Transform::kSkipInitialization);
+    bool didInvert = rootLayer->screenSpaceTransform().GetInverse(&transformToLayerSpace);
+    DCHECK(didInvert);
     for (Region::Iterator fillRects(fillRegion); fillRects.has_rect(); fillRects.next()) {
         // The root layer transform is composed of translations and scales only,
-        // no perspective, so mapping is sufficient.
+        // no perspective, so mapping is sufficient (as opposed to projecting).
         gfx::Rect layerRect = MathUtil::mapClippedRect(transformToLayerSpace, fillRects.rect());
         // Skip the quad culler and just append the quads directly to avoid
         // occlusion checks.
         scoped_ptr<SolidColorDrawQuad> quad = SolidColorDrawQuad::Create();
         quad->SetNew(sharedQuadState, layerRect, screenBackgroundColor);
         quadCuller.append(quad.PassAs<DrawQuad>(), appendQuadsData);
     }
 }
 
 bool LayerTreeHostImpl::calculateRenderPasses(FrameData& frame)
@@ skipping 749 matching lines @@
         return ScrollStarted;
     }
     return ScrollIgnored;
 }
 
 static gfx::Vector2dF scrollLayerWithViewportSpaceDelta(PinchZoomViewport* viewport, LayerImpl& layerImpl, float scaleFromViewportToScreenSpace, gfx::PointF viewportPoint, gfx::Vector2dF viewportDelta)
 {
     // Layers with non-invertible screen space transforms should not have passed the scroll hit
     // test in the first place.
     DCHECK(layerImpl.screenSpaceTransform().IsInvertible());
-    gfx::Transform inverseScreenSpaceTransform = MathUtil::inverse(layerImpl.screenSpaceTransform());
+    gfx::Transform inverseScreenSpaceTransform(gfx::Transform::kSkipInitialization);
+    bool didInvert = layerImpl.screenSpaceTransform().GetInverse(&inverseScreenSpaceTransform);
+    // TODO: With the advent of impl-side crolling for non-root layers, we may
+    // need to explicitly handle uninvertible transforms here.
+    DCHECK(didInvert);
 
     gfx::PointF screenSpacePoint = gfx::ScalePoint(viewportPoint, scaleFromViewportToScreenSpace);
 
     gfx::Vector2dF screenSpaceDelta = viewportDelta;
     screenSpaceDelta.Scale(scaleFromViewportToScreenSpace);
 
     // First project the scroll start and end points to local layer space to find the scroll delta
     // in layer coordinates.
     bool startClipped, endClipped;
     gfx::PointF screenSpaceEndPoint = screenSpacePoint + screenSpaceDelta;
@@ skipping 427 matching lines @@
     ScrollbarAnimationController* scrollbarController = layer->scrollbarAnimationController();
     double monotonicTime = (time - base::TimeTicks()).InSecondsF();
     if (scrollbarController && scrollbarController->animate(monotonicTime))
         m_client->setNeedsRedrawOnImplThread();
 
     for (size_t i = 0; i < layer->children().size(); ++i)
         animateScrollbarsRecursive(layer->children()[i], time);
 }
 
 }  // namespace cc