Remove rotation constraints

This should be an iOS SDK option, not hard coded into
low-level renderering.

Fixes #458

include/mbgl/map/map.hpp

@@ -115,7 +115,6 @@ public:
     void resetNorth();
     void startRotating();
     void stopRotating();
-    bool canRotate();
 
     // Debug
     void setDebug(bool value);

include/mbgl/map/transform.hpp

@@ -51,7 +51,6 @@ public:
     double getAngle() const;
     void startRotating();
     void stopRotating();
-    bool canRotate();
 
     // Transitions
     bool needsTransition() const;

src/map/map.cpp

@@ -551,10 +551,6 @@ void Map::stopRotating() {
     update();
 }
 
-bool Map::canRotate() {
-    return transform.canRotate();
-}
-
 
 #pragma mark - Toggles
 

src/map/transform.cpp

@@ -14,7 +14,6 @@ using namespace mbgl;
 
 const double D2R = M_PI / 180.0;
 const double M2PI = 2 * M_PI;
-const double MIN_ROTATE_SCALE = 8;
 
 Transform::Transform(View &view_)
     : view(view_)
@@ -37,7 +36,6 @@ bool Transform::resize(const uint16_t w, const uint16_t h, const float ratio,
         current.pixelRatio = final.pixelRatio = ratio;
         current.framebuffer[0] = final.framebuffer[0] = fb_w;
         current.framebuffer[1] = final.framebuffer[1] = fb_h;
-        if (!canRotate() && current.angle) _setAngle(0);
         constrain(current.scale, current.y);
 
         view.notify_map_change(MapChangeRegionDidChange);
@@ -286,9 +284,6 @@ void Transform::_setScaleXY(const double new_scale, const double xn, const doubl
 
     constrain(final.scale, final.y);
 
-    // Undo rotation at low zooms.
-    if (!canRotate() && current.angle) _setAngle(0);
-
     if (duration == 0) {
         current.scale = final.scale;
         current.x = final.x;
@@ -398,9 +393,6 @@ void Transform::_setAngle(double new_angle, const timestamp duration) {
 
     final.angle = new_angle;
 
-    // Prevent rotation at low zooms.
-    if (!canRotate()) final.angle = 0;
-
     if (duration == 0) {
         current.angle = final.angle;
     } else {
@@ -449,10 +441,6 @@ void Transform::_clearRotating() {
     }
 }
 
-bool Transform::canRotate() {
-    return (current.scale > MIN_ROTATE_SCALE);
-}
-
 #pragma mark - Transition
 
 bool Transform::needsTransition() const {