Oilpan: Improve address space randomization for the Oilpan heap.

Allocate oilpan heap pages in chunks of 10 pages at a random address.
Allocating all individual pages at random addresses blows out the TLB
and leads to poor performance so we group the allocations slightly.

Using a random aligned address for our allocations has the additional
advantage that we usually do not have to unmap surrounding unaligned
bits on all page allocations which turns out to be surprisingly
expensive on Linux.

The address space randomization code has been extracted from
PartitionAlloc. No need to reinvent the wheel. :-)

R=cevans@chromium.org, erik.corry@gmail.com, oilpan-reviews@chromium.org, tsepez@chromium.org

Review URL: https://codereview.chromium.org/343753004

git-svn-id: svn://svn.chromium.org/blink/trunk@177085 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Introduce builders for tracing event arguments

The builders provide interface for constructing JSON-like structure. Current implementation uses JSONValue as backing store but it may be replaced later with something more efficient without requiring to update client code.

Current implementation ensures that we create isolated copies of all strings as they may be destroyed on a different thread.

JSCallStack in InspectorTraceEvents.cpp now serializes call stack to string in the constructor instead of doing it later during tracing events serialization. Alternatively we could clone ScriptCallStack so that it contained isolated copies of all strings and do the serialization later but that seemed equally costly.

BUG=375242,361045

Review URL: https://codereview.chromium.org/357703002

git-svn-id: svn://svn.chromium.org/blink/trunk@177086 bbb929c8-8fbe-4397-9dbb-9b2b20218538
MediaQueryEvaluator getting mediaType from MediaValues

Current MediaQueryEvaluator takes the media type on top of the LocalFrame upon its creation.
That means that media type changes are not taken into account, and users such as
MediaQueryMatcher have to create a new instance whenever the media type may have changed.
This CL fixes that.

BUG=389462

Review URL: https://codereview.chromium.org/335313003

git-svn-id: svn://svn.chromium.org/blink/trunk@177087 bbb929c8-8fbe-4397-9dbb-9b2b20218538