PPC: Debugger: prepare code for debugging on a per-function basis.

Port 35c28ce0

Original commit message:
    Prior to this patch, we enter a global debug mode whenever a break point
    is set. By entering this mode, all code is deoptimized and activated
    frames are recompiled and redirected to newly compiled debug code.

    After this patch, we only deoptimize/redirect for functions we want to
    debug. Trigger for this is Debug::EnsureDebugInfo, and having DebugInfo
    object attached to the SFI prevents optimization/inlining.

    The result is that we can have optimized code for functions without break
    points alongside functions that do have break points, which are not
    optimized.

R=yangguo@chromium.org, dstence@us.ibm.com, michael_dawson@ca.ibm.com
BUG=v8:4132
LOG=N

Review URL: https://codereview.chromium.org/1244823002

Cr-Commit-Position: refs/heads/master@{#29764}

src/ppc/assembler-ppc-inl.h

@@ -375,8 +375,7 @@ void RelocInfo::Visit(Isolate* isolate, ObjectVisitor* visitor) {
   } else if (RelocInfo::IsCodeAgeSequence(mode)) {
     visitor->VisitCodeAgeSequence(this);
   } else if (RelocInfo::IsDebugBreakSlot(mode) &&
-             IsPatchedDebugBreakSlotSequence() &&
-             isolate->debug()->has_break_points()) {
+             IsPatchedDebugBreakSlotSequence()) {
     visitor->VisitDebugTarget(this);
   } else if (IsRuntimeEntry(mode)) {
     visitor->VisitRuntimeEntry(this);
@@ -400,8 +399,7 @@ void RelocInfo::Visit(Heap* heap) {
     StaticVisitor::VisitInternalReference(this);
   } else if (RelocInfo::IsCodeAgeSequence(mode)) {
     StaticVisitor::VisitCodeAgeSequence(heap, this);
-  } else if (heap->isolate()->debug()->has_break_points() &&
-             RelocInfo::IsDebugBreakSlot(mode) &&
+  } else if (RelocInfo::IsDebugBreakSlot(mode) &&
              IsPatchedDebugBreakSlotSequence()) {
     StaticVisitor::VisitDebugTarget(heap, this);
   } else if (IsRuntimeEntry(mode)) {