[3171580] Fix two typos related to fixed-size buffers

mFixedSize was never set, this bug was introduced during some "cleanup", in
practice this could cause some issues when a fixed-size buffer was used and
the window was resized.

Layer::drawForSreenShot() had a typo that had no effect.

mFixedSize was used to determine if filtering was needed, which was a bit too
conservative and created a dependency between filtering and "fixed size" states
which should exist.

Now we enable filtering based on the size of the buffer vs. the size of the layer.

Change-Id: I32044e91b0c944c1b137efdceb3f01dfaa78119d
diff --git a/services/surfaceflinger/LayerBase.cpp b/services/surfaceflinger/LayerBase.cpp
index 64eed4b..79c6d0d 100644
--- a/services/surfaceflinger/LayerBase.cpp
+++ b/services/surfaceflinger/LayerBase.cpp
@@ -216,14 +216,10 @@
         flags |= eVisibleRegion;
         this->contentDirty = true;
 
-        mNeedsFiltering = false;
-        if (!(mFlags & DisplayHardware::SLOW_CONFIG)) {
-            // we may use linear filtering, if the matrix scales us
-            const uint8_t type = temp.transform.getType();
-            if (!temp.transform.preserveRects() || (type >= Transform::SCALE)) {
-                mNeedsFiltering = true;
-            }
-        }
+        // we may use linear filtering, if the matrix scales us
+        const uint8_t type = temp.transform.getType();
+        mNeedsFiltering = (!temp.transform.preserveRects() ||
+                (type >= Transform::SCALE));
     }
 
     // Commit the transaction